Identification of procollagen mRNAs transferred to diazobenzyloxymethyl paper from formaldehyde agarose gels

The pattern of RNA integrity and the expression of housekeeping genes are influenced by sodium hypochlorite and ascorbic acid

BACKGROUND

Basic biological science research deals with nucleic acid isolation. Post-isolation nucleic acid integrity has a pivotal role in further elucidating gene expression and other molecular mechanisms. RNA (ribonucleic acid), cDNA (complementary deoxyribonucleic acid), and PCR (Polymerase chain reaction) products' integrity and quality are affected by several factors in biochemical and biophysical degradation modes. Inadequate evidence was noted about the direct effects of sodium hypochlorite and L-ascorbic acid.

OBJECTIVES

This study aims to test the effects of sodium hypochlorite (SHC) and L-ascorbic acid (LAA) in total RNA and PCR products, respectively, in an acellular condition.

METHODS

The study was categorized into three steps total RNA, cDNA, and PCR product evaluations. mBM-MSCs were used to extract RNA and then treated with SHC. Crude total RNA and, after DNase 1 treatment, the bands of total RNA samples were visualized by agarose gel electrophoresis. cDNAs were synthesized from SHC-treated (0.25%) and untreated RNAs, which were also expressed on the gel. LAA (5 µM, 15 µM, 25 µM, and 50 µM) were added to cDNAs synthesized from SHC- and non-SHC-treated samples. Housekeeping genes, Gapdh (Glyceraldehyde 3-phosphate dehydrogenase), and 18S rRNA (18S Ribosomal ribonucleic acid) were amplified in both groups.

RESULTS

SHC-treated samples produced clearer bands on an agarose gel. Its treatment did not affect the integrated densities of agarose bands which revealed non-significant (P ≤ 0.05) differences in SHC-treated, untreated RNA, and cDNA. However, significant variations were observed at the PCR level. SHC-treated samples expressed decreased housekeeping gene expression in amplified products (Gapdh and 18S rRNA) and slightly but non-significantly high band intensities appeared in the presence of LAA. Significant variable differences (*P ≤ 0.05) were observed between SHC-treated and non-treated groups after LAA treatment.

CONCLUSIONS

SHC (0.25%) is favorable in removing RNases and maintaining the integrity of RNA. cDNA synthesis did not affect by SHC treatment, and it follows the same as untreated samples after DNase 1 treatment. LAA drew a positive impact to improve the quality of PCR products in terms of band intensities, which is insignificant in SHC-treated RNA. Interestingly, it was revealed from our study that 5-25 µM LAA has the most beneficial role in the acquisition of PCR products, i.e. gene expression. These concentrations can be safely used to improve the quality of gene expression. This phenomenon can be used to achieve other, rarer, desired gene expressions. Further research is needed to explore the effects of SHC on the acquisition of PCR products using other solutions.

Analysis of RNA by Northern Blotting

Northern hybridization is used to measure the amount and size of RNAs transcribed from eukaryotic genes and to estimate their abundance. No other method is capable of obtaining these pieces of information simultaneously from a large number of RNA preparations; northern analysis is therefore fundamental to studies of gene expression in eukaryotic cells. To prepare a northern blot for hybridization, RNA must be separated according to size through a denaturing agarose or polyacrylamide gel and transferred to a solid support in a way that preserves its topological distribution within the gel. These important steps in northern analysis are discussed here.

Separation of RNA according to Size: Electrophoresis of RNA through Agarose Gels Containing Formaldehyde

Samples of RNA may be denatured by treatment with formamide and separated by electrophoresis through agarose gels containing formaldehyde. In this method, RNA is fractionated by electrophoresis through an agarose gel containing 2.2 m formaldehyde.

Spermatozoa Transcriptional Response and Alterations in PL Proteins Properties after Exposure of Mytilus galloprovincialis to Mercury

Mercury (Hg) is an environmental pollutant that impacts human and ecosystem health. In our previous works, we reported alterations in the properties of Mytilus galloprovincialis protamine-like (PL) proteins after 24 h of exposure to subtoxic doses of toxic metals such as copper and cadmium. The present work aims to assess the effects of 24 h of exposure to 1, 10, and 100 pM HgCl₂ on spermatozoa and PL proteins of Mytilus galloprovincialis. Inductively coupled plasma–mass spectrometry indicated accumulation of this metal in the gonads of exposed mussels. Further, RT-qPCR analyses showed altered expression levels of spermatozoa mt10 and hsp70 genes. In Mytilus galloprovincialis, PL proteins represent the major basic component of sperm chromatin. These proteins, following exposure of mussels to HgCl₂, appeared, by SDS-PAGE, partly as aggregates and showed a decreased DNA-binding capacity that rendered them unable to prevent DNA damage, in the presence of CuCl₂ and H₂O₂. These results demonstrate that even these doses of HgCl₂ exposure could affect the properties of PL proteins and result in adverse effects on the reproductive system of this organism. These analyses could be useful in developing rapid and efficient chromatin-based genotoxicity assays for pollution biomonitoring programs.

Protocols for Northern Analysis of Exosome Substrates and Other Noncoding RNAs

Over the past decade a plethora of noncoding RNAs (ncRNAs) have been identified, initiating an explosion in RNA research. Although RNA sequencing methods provide unsurpassed insights into ncRNA distribution and expression, detailed information on structure and processing are harder to extract from sequence data. In contrast, northern blotting methods provide uniquely detailed insights into complex RNA populations but are rarely employed outside specialist RNA research groups. Such techniques are generally considered difficult for nonspecialists, which is unfortunate as substantial technical advances in the past few decades have solved the major challenges. Here we present simple, reproducible and highly robust protocols for separating glyoxylated RNA on agarose gels and heat denatured RNA on polyacrylamide-urea gels using standard laboratory electrophoresis equipment. We also provide reliable transfer and hybridization protocols that do not require optimization for most applications. Together, these should allow any molecular biology lab to elucidate the structure and processing of ncRNAs of interest.

Molecular effects on spermatozoa of Mytilus galloprovincialis exposed to hyposaline conditions

Salinity represents a critical environmental and an ecological factor in the reproduction of marine species. As global climate changes and anthropogenic factors affect salinity, in this study, we have analyzed the responses of Mytilus galloprovincialis spermatozoa to hyposaline stress. We exposed mussels, in laboratory tanks, for 24 hr at 18°C to control (35.9 psu) and three hyposaline (17.1, 22.6, and 26.2 psu) conditions, and evaluated the expression of sperm hsp70 and protamine-like proteins genes. Further we analyzed the electrophoretic pattern, the DNA binding and the release from sperm nuclei of protamine-like proteins. For all experimental approaches used, the results obtained at 17.1 psu condition were very similar to those obtained in the control condition, while alterations were always recorded at 22.6 and 26.2 psu conditions. Particularly, at 22.6 and 26.2 psu, was observed: 42.5- and 17.1-fold increase in hsp70 expression, respectively, and hypoexpression of PL-II/PLIV protamine-like proteins genes. Further, electrophoretic mobility shift assays and salt-induced release of nuclear proteins from sperm nuclei, revealed alterations in the PL proteins/DNA binding, in these two hyposaline conditions. The similarity between the results obtained in control and in the more severe hyposaline condition (17.1 psu) could indicate a phenomenon of fertility preservation strategy due to gamete plasticity.

Frog (Pelophylax bergeri, Günther 1986) endocrine disruption assessment: characterization and role of skin poly(ADP-ribose) polymerases

Model of the our research was the adult male amphibian anura, Pelophylax bergeri, poikilotherm species not considered threatened by the IUCN, sampled in representative sites at different degree. In the first phase, a biochemical characterization of the ADP-ribosylation on the skin of barcoded amphibian anura collected from Matese Lake (clean reference site in CE, Italy) was carried out. Two PARP isoforms were evidence: the first of 66 kDa is localized into nucleus and activated by DNA damage; the second of 150 kDa is in cytoplasm, as demonstrated by biochemical and immunohistochemical analysis. Subsequently, the PARP activity, the quantitative expression of androgen receptor gene, and the levels of arsenic and chromium in skin and testis of frog and soil, water, and sediment collected from sites at different degrees of pollution were measured. A significant variation of PARP activity and androgen receptor expression levels was detected in both tissues of barcoded frogs from Sarno and Scafati, along Sarno River (SA, Italy), suggesting that a PARP activation is correlated to pollution and to steroid-regulated physiology disruption.

Reactive oxygen species and glutathione antioxidants in the testis of the soil biosentinel Podarcis sicula (Rafinesque 1810)

Important toxicological achievements have been made during the last decades using reptiles. We focus our investigation on gonadal reproductive health of the soil biosentinel Podarcis sicula which is very sensitive to endocrine-disrupting chemicals. The aim of this study is to quantitatively detect, by sensitive microassays, reactive oxygen species and the glutathione antioxidants in the testis and investigate if they are differentially expressed before and after remediation of a site of the "Land of Fires" (Campania, Italy) subject to illicit dumping of unknown material. The oxidative stress level was evaluated by electron spin resonance spectroscopy applying a spin-trapping procedure able to detect products of lipid peroxidation, DNA damage and repair by relative mobility shift, and poly(ADP-ribose) polymerase enzymatic activity, respectively, the expression of glutathione peroxidase 4 transcript by real-time quantitative PCR analysis, the antioxidant glutathione S-transferase, a well-assessed pollution index, by enzymatic assay and the total soluble antioxidant capacity. Experimental evidences from the different techniques qualitatively agree, thus confirming the robustness of the combined experimental approach. Collected data, compared to those from a reference unpolluted site constitute evidence that the reproductive health of this lizard is impacted by pollution exposure. Remediation caused significant reduction of reactive oxygen species and downregulation of glutathione peroxidase 4 mRNAs in correspondence of reduced levels of glutathione S-transferase, increase of antioxidant capacity, and repair of DNA integrity. Taken together, our results indicate directions to define new screening approaches in remediation assessment.

Mytilus galloprovincialis (Lamarck, 1819) spermatozoa: hsp70 expression and protamine-like protein property studies

In this work, we describe results of the reproductive health monitoring studies in Mytilus galloprovincialis following spermatozoa hsp70 expression and protamine-like protein properties. Mussels control (ctr) were released within cages for 30 days in three different marine sites near Naples (Campania, Italy): Bagnoli south (BAs) and Bagnoli north (BAn), both close to a disposal metallurgical factory and in Capo Miseno (CM). Studies of hsp70 gene expression carried out, by RT-qPCR, in mussel spermatozoa have shown varied expression levels, particularly 5, 13, and 15-fold more than ctr in CM, BAs, and BAn, respectively, indicating highest involvement of stress proteins in spermatozoa of mussels in Bagnoli. In order to evaluate the possible risk on Mytilus galloprovincialis sustainability loss, electrophoretic analyses were performed on protamine-like proteins (PL) of collected spermatozoa. The results showed that CM PL were apparently unaltered with respect to ctr PL, while BAs and BAn PL appeared in part in the form of peptides and in part as bands with low mobility. Further, CM and BAs PL showed, by electrophoretic mobility shift assay, a decrease in DNA binding ability and a change in their DNA binding mode. The results of this investigation show the usefulness of the study of alterations of spermatozoa hsp70 expression and protamine-like protein properties for eco-toxicological evaluation using Mytilus galloprovincialis as a bioindicator.

Quantification and quality control of a small non-coding RNA preparation

Recent advances in high-throughput sequencing have shed some new light on the diversity of small non-coding RNA (sncRNA) classes and their crucial role in gene regulation and diseases. RNA quantification and control of RNA integrity are two key steps in sncRNA profiling. In this chapter, we will describe different gold standard methods used to achieve both purposes before the use of the RNAs in downstream applications.

DNA insertions which affect the expression of the yeast iso-2-cytochrome c gene

The plasmid YCpCYC7(2) was constructed containing the Saccharomyces cerevisiae CYC7 gene, encoding the iso-2-cytochrome c protein, replicative sequences and selective markers from both E. coli and yeast, and the centromere of yeast chromosome III. The expression of the plasmid-CYC7 gene in yeast was similar to the low level expression characteristic of the chromosomal CYC7 gene. A number of insertions into the sequences 5' to the gene were constructed in vitro. The insertion at 142 by 5' to the coding sequence of a 400 by fragment which lies 5' to the CYC1 gene and is known to be essential for the high rates of CYC1 transcription increased transcription of the CYC7 gene to levels characteristic of CYC1 transcription. On the other hand, the insertion of random DNA fragments at the same position gave mostly decreased CYC7 transcription. In addition to these in vitro constructions, a mutant plasmid was selected which had increased CYC7 transcription. This mutation was caused by the insertion of the bacterial IS1 element 313 by 5' to the CYC7 coding sequence. The significance of these results is discussed in terms of two alternative models for CYC7 gene expression.

Control of multicellular development by the physically interacting deneddylases DEN1/DenA and COP9 signalosome

Deneddylases remove the ubiquitin-like protein Nedd8 from modified proteins. An increased deneddylase activity has been associated with various human cancers. In contrast, we show here that a mutant strain of the model fungus Aspergillus nidulans deficient in two deneddylases is viable but can only grow as a filament and is highly impaired for multicellular development. The DEN1/DenA and the COP9 signalosome (CSN) deneddylases physically interact in A. nidulans as well as in human cells, and CSN targets DEN1/DenA for protein degradation. Fungal development responds to light and requires both deneddylases for an appropriate light reaction. In contrast to CSN, which is necessary for sexual development, DEN1/DenA is required for asexual development. The CSN-DEN1/DenA interaction that affects DEN1/DenA protein levels presumably balances cellular deneddylase activity. A deneddylase disequilibrium impairs multicellular development and suggests that control of deneddylase activity is important for multicellular development.

The family of small ubiquitin-like (Ubl) proteins plays a major role in the control of stability, activity, or localization of modified target proteins in a eukaryotic cell. Lysine side chains are modified by covalent Ubl attachment, and this process can be reversed by specific proteases. Nedd8 is the closest relative to ubiquitin in the Ubl family. We describe here a novel, conserved interplay between two physically interacting deneddylases that are specific for Nedd8. Increased deneddylase activity had been shown to be associated with human cancers. We convey here specific distinct developmental functions of the two deneddylases in multicellular differentiation of the filamentous fungus Aspergillus nidulans. The physical interaction between both proteins affects protein stability and therefore cellular deneddylase activity. The equilibrium between the two deneddylases and their physical interaction are conserved from fungi to human and seem to be important for normal development of a multicellular organism. These findings open a different angle for future studies of tumor formation in humans.

Bleach gel: a simple agarose gel for analyzing RNA quality

RNA-based applications requiring high-quality, non-degraded RNA are a foundational element of many research studies. As such, it is paramount that the integrity of experimental RNA is validated prior to cDNA synthesis or other downstream applications. In the absence of expensive equipment such as microfluidic electrophoretic devices, and as an alternative to the costly and time-consuming standard formaldehyde gel, RNA quality can be quickly analyzed by adding small amounts of commercial bleach to TAE buffer-based agarose gels prior to electrophoresis. In the presence of low concentrations of bleach, the secondary structure of RNA is denatured and potential contaminating RNases are destroyed. Because of this, the 'bleach gel' is a functional approach that addresses the need for an inexpensive and safe way to evaluate RNA integrity and will improve the ability of researchers to rapidly analyze RNA quality.

Induction of phenylalanine ammonia-lyase and 4-coumarate:CoA ligase mRNAs in cultured plant cells by UV light or fungal elicitor

The mRNAs encoding two enzymes of phenylpropanoid metabolism, phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) and 4-coumarate:CoA ligase (4CL; EC 6.2.1.12), were induced in cultured parsley cells (Petroselinum hortense) either by irradiation with UV light or by treatment with elicitor, a cell-wall fraction of the fungus Phytophthora megasperma f. sp. glycinea. Two-dimensional gel electrophoresis of the encoded PAL and 4CL proteins revealed that the mRNAs induced by either treatment were very similar if not identical. RNA blot hybridization with cDNAs complementary to these mRNAs was used to measure changes in the mRNA amounts at various times after either treatment. Total cellular PAL and 4CL mRNA amounts increased coordinately after UV irradiation to a maximum at 7 hr and then decreased to uninduced levels by 30 hr with the same kinetics as observed previously for the changes in the translational activities. Treatment with the fungal elicitor also caused coordinated, but more rapid, changes in PAL and 4CL mRNA translational activities, with a sharp peak occurring 3 hr after the addition of elicitor. Corresponding changes in mRNA amounts were observed only for 4CL, whereas the amount of PAL mRNA continued to increase at least up to 20 hr after elicitor addition. Our results suggest that parsley cells respond to UV irradiation or addition of fungal elicitor by increased rates of transcription of genes involved in the synthesis of compounds related to UV or disease resistance, respectively.

Isolation of cloned cDNAs to auxin-responsive poly(A)RNAs of elongating soybean hypocotyl

Auxin-responsive cDNA clones have been isolated from a cDNA library prepared from elongating soybean hypocotyl poly(A)(+)RNA. The expression of two such sequences has been assessed by RNA blot hybridization analyses during normal developmental transitions in the soybean hypocotyl and during incubation of sections excised from the region of cell elongation. The concentrations of these poly(A)(+)RNAs are higher in the elongating zone than in the apical and mature zones of the hypocotyl. Both poly(A)(+)RNAs are depleted during incubation of the sections in the absence of auxin. The loss of one of these sequences (pJCW1) is prevented by the addition of auxin to the incubation medium while the other sequence (pJCW2) increases above the initial level in the presence of auxin. The addition of auxin to auxin-depleted tissue in which the sequences are depleted results in rapid accumulation of these poly(A)(+)RNAs; pJCW1 accumulates to the control level while pJCW2 increases well above the control level. These data along with others [Baulcombe, D. C. & Key, J. L. (1980) J. Biol. Chem. 255, 8907-8913] demonstrate directly a highly selective effect of auxin on the expression of a small number of mRNAs in tissues undergoing both cell elongation and cell division in response to auxin. Although the data are suggestive of a close association betwen auxin action and altered gene expression, a causal relationship is not established. It seems highly unlikely, however, that such specific effects of auxin on gene expression are unimportant in auxin physiology.

Transcription of the white locus in Drosophila melanogaster

Genetic studies of the white locus have shown that it has a distal region where structural mutations occur and a proximal region where regulatory mutations occur. To better understand the molecular basis of this genetic organization we have analyzed white locus transcription. A 2.7-kilobase transcript comprising 0.0005% of poly(A)-RNA was detected in RNA prepared from pupae or adults. The structure of this transcript helps clarify some unusual genetic properties of the locus. There is a small 5' exon separated from the majority of the sequences found in the mature RNA by an intron of approximately 2.8 kilobases. This 5' exon is from the proximal region of the locus, whereas the main body of the RNA maps to the distal region. The mutationally silent region between the proximal and distal regions corresponds to the large intron. We have identified the family and determined the exact location of a number of transposable element insertions within the locus. These results show that transposable element insertions within introns can be without phenotypic effect. We have also investigated the effect on the white transcript of the zeste mutation, which represses white locus expression as judged by eye color phenotype. The RNA was unchanged in size or abundance in poly(A)-RNA from adult flies. This demonstrates that the zeste-white interaction does not occur by simply repressing transcription of the white locus in all tissues.

Nucleotide sequence of F(0)-ATPase proteolipid (subunit 9) gene of maize mitochondria

The F(0)-ATPase proteolipid, also referred to as subunit 9 or the dicyclohexylcarbodiimide-binding protein, is encoded by a mitochondrial gene in maize that we have designated atp 9. The clone containing atp 9 was selected for investigation from a mitochondrial DNA library because of its abundant transcript in total maize mitochondrial RNA preparations. Sequence analysis of the clone revealed an open reading frame that was readily identified by its nucleotide homology with the ATPase subunit 9 gene of yeast. As deduced from the nucleotide sequence, the maize ATPase subunit 9 protein contains 74 amino acids with a molecular weight of 7368. Substantial amino acid sequence homology is conserved among maize, yeast, bovine, and Neurospora mitochondrial ATPase subunit 9 proteins, regardless of whether the gene is nuclearly encoded (bovine and Neurospora) or mitochondrially encoded (yeast and maize). RNA transfer blot analysis indicated that the gene sequence is actively transcribed, producing an initial transcript that is large and extensively processed.

4-dihydrotrisporin-dehydrogenase, an enzyme of the sex hormone pathway of Mucor mucedo: purification, cloning of the corresponding gene, and developmental expression

The NADP-dependent 4-dihydrotrisporin-dehydrogenase is a (-) mating-type-specific enzyme in the pathway from beta-carotene to trisporic acid. This substance and its isomers and derivatives represent the general system of sexual communication in zygomycetes. The (-) mating type of Mucor mucedo was stimulated by trisporic acid and the enzyme was purified by ion exchange and affinity chromatography. Several peptides of the 26-kDa protein, digested with trypsin, were sequenced by mass spectrometry. Oligonucleotides based on protein sequence data were used for PCR amplification of genomic DNA. The primary PCR fragment was sequenced and the complete gene, TSP2, was isolated. A labeled TSP2 hybridization probe detects a single-copy gene in the genome of M. mucedo. Northern blot analysis with RNAs from different growth stages reveals that the expression of the gene depends on the developmental stage of the mycelium in both mating types of M. mucedo. At the enzyme level, activity is found exclusively in the (-) mating type. However, renaturation of proteins in sodium dodecyl sulfate-containing gels revealed the TSP2 gene product in both mating types. Analyzing the protein sequence places the enzyme in the short chain dehydrogenase superfamily. Thus, it has an evolutionary origin distinct from that of the previously isolated 4-dihydromethyltrisporate dehydrogenase, which belongs to the aldo/keto reductase superfamily. Apart from the TSP2 genes in the three sequenced zygomycetous genomes (Phycomyces blakesleeanus, Rhizopus oryzae, and Mucor circinelloides), the closest relative is the Myxococcus xanthus CsgA gene product, which is also a short chain dehydrogenase, involved in C signaling and fruiting body formation.

Effects of dexamethasone on insulin receptor in aging

The aim of this study was to examine the effects of dexamethasone (Dex) on functional properties of the rat insulin receptor (IR). Male Mill Hill hooded rats, 3, 6, 12, 18 and 21 months old, were injected with Dex (4 mg/kg) and rat liver and erythrocytes were used for experiments 18 h after Dex administration. Treatment with Dex lowered the specific binding (SB) of insulin (INS) in the liver of 3- and 18-month-old rats and concentration of INS binding sites (N1, N2) and the dissociation constant of low-affinity binding sites (Kd2) in the liver of 6- and 18-month-old rats. In addition, Dex treatment lowered the liver IR protein level in all analyzed groups, except 21-month-old rats where it remained unchanged, but raised the IR mRNA level in 18-month-old rats. In erythrocytes, treatment with Dex decreased SB and Kd2 (in animals 3 and 6 months old) and N1 (in ones 3 and 18 months old). Following Dex treatment, the INS plasma level increased (in rats 3, 18 and 21 months old), while glucose (Glu) concentration increased in 3 and 12 months old, but decreased in 6- and 21-month-old rats. In summary, Dex exerts the strongest effect on the erythrocyte IR of 3- and 6-month-old rats and the hepatic IR of 18-month-old rats. IR in both tissues is almost insensitive to Dex in 12- and 21-month-old rats. The pattern of age-related changes of IR induced by Dex does not correlate with changes of plasma Glu and INS.

Northern analysis of sense and antisense frequency RNA in Neurospora crassa

In Northern analysis the presence of specific RNA transcripts is detected and their quantity can be estimated. RNA is separated using denaturing agarose gel electrophoresis and is subsequently transferred and fixed to a solid support, such as a nitrocellulose filter. When labeled probes are hybridized to these immobilized RNA molecules, their presence can be visualized by autoradiography. Here we describe Northern hybridization using radioactively labeled riboprobes to show circadian expression of endogenous sense and antisense frequency RNA in the filamentous fungus Neurospora crassa.

Age-related changes of insulin receptors, plasma insulin and glucose level

The effects of aging on hepatic and erythrocyte insulin receptors have been investigated in 6, 12, 18 and 21-months-old compare to 3-months-old rats. Plasma insulin was elevated in 6, 12 and 18-months-old rats. Specific binding of insulin in liver was increased at the age of 8 months and accompanied with increase in concentration of low affinity binding sites, while specific binding to erythrocytes as well as concentration of both classes of binding sites was increased in 6-months-old rats. The protein and mRNA content of hepatic receptor were decreased only in the oldest animals. Plasma glucose was elevated starting from 12-months-old rats, while, after decrease in 6-months-old animals, citrulline was raised in the oldest group. The results demonstrating that specific binding of insulin in liver and erythrocytes and the concentration of binding sites in both tissues were not decreased during aging, as well as the absence of changes in affinity of insulin binding sites do not point out to occurrence of insulin resistance. However, the increase in insulinemia in the middle of lifespan, elevated plasma glucose and citrulline as well as decrease of hepatic receptor protein and mRNA content in the oldest animals indicate some age-related changes in insulin signaling.

The COP9 signalosome is an essential regulator of development in the filamentous fungus Aspergillus nidulans

The COP9 signalosome (CSN) is a conserved multiprotein complex involved in regulation of eukaryotic development. The deduced amino acid sequences of two Aspergillus nidulans genes, csnD and csnE, show high identities to the fourth and fifth CSN subunits of higher eukaryotes. The csnD transcript is abundant during vegetative growth as well as development and the corresponding protein accumulates in the nucleus. Strains deleted for either csn gene are viable and show identical mutant phenotypes at conditions that allow development: hyphae appear partly red and contain cells of reduced size. Additionally, light dependence of propagation onset is affected. The Delta csn mutants are capable of initiating the sexual cycle and develop primordia, but maturation to sexual fruit bodies is blocked. This developmental arrest could not be overcome by overexpression of the sexual activator velvet (VEA). We conclude that the COP9 signalosome in A. nidulans is a key regulator of sexual development, and its proposed structural and functional conservation to the CSN of higher eukaryotes enables studies on this regulatory complex in a genetically amenable organism.

Betaine homocysteine methyltransferase: gene cloning and expression analysis in rat liver cirrhosis

It has been known for over half a century that homocysteine levels are elevated in liver cirrhosis, but the basis for it is not fully understood. Using differential display, we identified betaine homocysteine methyltransferase (BHMT) as a gene down-regulated in rat liver cirrhosis and most likely involved in this dysregulation. A partial BHMT clone was isolated by screening of a cDNA library with the differential display fragment. The full-length gene was generated by primer extension of cDNA. Expression levels of BHMT in cirrhotic livers of bile duct ligated rats were compared to controls by Northern and Western blotting as well as by enzyme activity measurements. BHMT mRNA levels were reduced to 29+/-23% in established liver cirrhosis induced by bile duct ligation (BDL) as compared to controls. Enzyme assays in crude liver homogenates showed a similar reduction in BHMT activity in bile duct ligated rat livers. By Western blotting, BHMT could be detected in crude liver homogenates of control animals, but was reduced to below the limit of detection in cirrhotic livers. In conclusion, these findings establish a reduced BHMT enzyme activity in cirrhotic rat livers, which may explain the elevated plasma homocysteine levels in cirrhosis.

Corticosteroid-binding globulin synthesis and distribution in rat white adipose tissue

Corticosterone binding (CB) capacity was determined in visceral and subcutaneous white adipose tissue (WAT), as well as in plasma of lean Zucker rats. Perfusion of rats with saline eliminated most liver and kidney corticosterone binding but did not affect CB in WAT. The cytosol extracts of isolated cells, however, did not bind corticosterone in detectable amounts. By means of a RT-PCR procedure it was found that corticosterone-binding globulin (CBG) was expressed in WAT. By immunohistochemical detection in WAT sections, CBG was seen in a thin layer surrounding the cells near the plasma membrane. These data suggest that the CBG layer surrounding the cells may act as a protective barrier limiting the access of glucocorticoids to adipocytes.

A highly basic N-terminal extension of the mitochondrial matrix enzyme ornithine transcarbamylase from rat liver

We have deduced the amino acid sequence of the N-terminal leader peptide of the mitochondrial enzyme ornithine transcarbamylase from a cDNA clone obtained from a rat liver cDNA library. The sequence is remarkable in being highly basic, having 4 arginine, 3 lysine and 1 histidine with no acidic residues in a total of 32 residues. The leader sequence has no extensive hydrophobic stretches, has 72% homology with the leader peptide of human ornithine transcarbamylase [1], and in terms of its basic character resembles the N-terminal extensions on a number of fungal mitochondrial [2-5] and pea chloroplast [6] proteins. Thus the basic nature of these leader peptides may constitute the signal for mitochondrial import.

Coevolution of transcriptional and allosteric regulation at the chorismate metabolic branch point of Saccharomyces cerevisiae

Control of transcription and enzyme activities are two interwoven regulatory systems essential for the function of a metabolic node. Saccharomyces cerevisiae strains differing in enzyme activities at the chorismate branch point of aromatic amino acid biosynthesis were constructed by recombinant DNA technology. Expression of an allosterically unregulated, constitutively activated chorismate mutase encoded by the ARO7(T226I) (ARO7(c)) allele depleted the chorismate pool. The resulting tryptophan limitation caused growth defects, which could be counteracted only by transcriptional induction of TRP2 encoding the competing enzyme anthranilate synthase. ARO7 expression is not transcriptionally regulated by amino acids. Transcriptional activation of the ARO7(c) allele led to stronger growth retardation upon tryptophan limitation. The same effect was achieved by removing the competing enzyme anthranilate synthase, which is encoded by the TRP2 gene, from the transcriptional control. The allelic situation of ARO7(c) being under general control instead of TRP2 resulted in severe growth defects when cells were starved for tryptophan. In conclusion, the specific regulatory pattern acting on enzymatic activities at the first metabolic node of aromatic amino acid biosynthesis is necessary to maintain proper flux distribution. Therefore, the evolution of the sophisticated allosteric regulation of yeast chorismate mutase requires as prerequisite (i) that the encoding ARO7 gene is not transcriptionally regulated, whereas (ii) the transcription of the competing feedback-regulated anthranilate synthase-encoding gene is controlled by availability of amino acids.

HARO7 encodes chorismate mutase of the methylotrophic yeast Hansenula polymorpha and is derepressed upon methanol utilization

The HARO7 gene of the methylotrophic, thermotolerant yeast Hansenula polymorpha was cloned by functional complementation. HARO7 encodes a monofunctional 280-amino-acid protein with chorismate mutase (EC 5.4. 99.5) activity that catalyzes the conversion of chorismate to prephenate, a key step in the biosynthesis of aromatic amino acids. The HARO7 gene product shows strong similarities to primary sequences of known eukaryotic chorismate mutase enzymes. After homologous overexpression and purification of the 32-kDa protein, its kinetic parameters (k(cat) = 319.1 s(-1), n(H) = 1.56, [S](0.5) = 16.7 mM) as well as its allosteric regulatory properties were determined. Tryptophan acts as heterotropic positive effector; tyrosine is a negative-acting, heterotropic feedback inhibitor of enzyme activity. The influence of temperature on catalytic turnover and the thermal stability of the enzyme were determined and compared to features of the chorismate mutase enzyme of Saccharomyces cerevisiae. Using the Cre-loxP recombination system, we constructed mutant strains carrying a disrupted HARO7 gene that showed tyrosine auxotrophy and severe growth defects. The amount of the 0.9-kb HARO7 mRNA is independent of amino acid starvation conditions but increases twofold in the presence of methanol as the sole carbon source, implying a catabolite repression system acting on HARO7 expression.

Circadian oscillation of photopigment transcript levels in the mouse retina

The mammalian retina contains an autonomous circadian oscillator that can sustain rhythms in outer segment disc shedding and melatonin synthesis even in the absence of cues from the central oscillator in the suprachiasmatic nucleus (SCN). The present investigation aimed to ascertain whether the steady-state levels of rod and cone opsin mRNA exhibited a circadian oscillation in the mouse, and if so, to characterise this oscillation with regard to phase. Retinas were collected from mice free-running in constant darkness at circadian times (CT) 0, 4, 12, 16, and 20. RNA was extracted for the production of Northern blots, which were sequentially hybridised with probes for alpha-tubulin (control), ultraviolet opsin, and rhodopsin. Whereas no significant oscillation was detected in the levels of alpha-tubulin, the levels of both ultraviolet opsin and rhodopsin transcripts oscillated with an amplitude of at least 3-fold. The highest levels were found at around CT12 (which corresponds to the subjective evening, the time of activity onset in the mouse). These results show that the levels of rod and cone photopigment mRNA are under circadian control. The significance of the rhythms and their phasing is discussed. These findings have potential clinical implications both with regard to nocturnal light treatment of phase asynchrony, and in the timing of chemo- and radiotherapy.

Suppressors of cdc25p overexpression identify two pathways that influence the G2/M checkpoint in fission yeast

Checkpoints maintain the order of cell-cycle events. At G2/M, a checkpoint blocks mitosis in response to damaged or unreplicated DNA. There are significant differences in the checkpoint responses to damaged DNA and unreplicated DNA, although many of the same genes are involved in both responses. To identify new genes that function specifically in the DNA replication checkpoint pathway, we searched for high-copy suppressors of overproducer of Cdc25p (OPcdc25(+)), which lacks a DNA replication checkpoint. Two classes of suppressors were isolated. One class includes a new gene encoding a putative DEAD box helicase, suppressor of uncontrolled mitosis (sum3(+)). This gene negatively regulates the cell-cycle response to stress when overexpressed and restores the checkpoint response by a mechanism that is independent of Cdc2p tyrosine phosphorylation. The second class includes chk1(+) and the two Schizosaccharomyces pombe 14-3-3 genes, rad24(+) and rad25(+), which appear to suppress the checkpoint defect by inhibiting Cdc25p. We show that rad24Delta mutants are defective in the checkpoint response to the DNA replication inhibitor hydroxyurea at 37 degrees and that cds1Delta rad24Delta mutants, like cds1Delta chk1Delta mutants, are entirely checkpoint deficient at 29 degrees. These results suggest that chk1(+) and rad24(+) may function redundantly with cds1(+) in the checkpoint response to unreplicated DNA.

Adrenalectomy and dexamethasone treatment alter the patterns of basal and acute phase response-induced expression of acute phase protein genes in rat liver

Hormonal requirements for full hepatic expression of alpha2-macroglobulin (alpha2M), alpha1-acid glycoprotein (AGP), haptoglobin (Hp) and gamma-fibrinogen (Fb) were assessed at the level of mRNA. Prior to exposure to turpentine-induced inflammation, rats were either depleted of glucocorticoids by adrenalectomy or supplemented with an excess of dexamethasone. Adrenalectomy alone did not affect the basal level of acute phase protein (APP) expression except for alpha2M mRNA, the level of which was enhanced. In contrast, dexamethasone treatment alone promoted full induction of alpha2M, significant, but not maximal increase of AGP and Hp mRNAs and suppression of Fb. In adrenalectomized rats, acute phase (AP)-cytokines, released in response to inflammation, promoted full expression of Fb and Hp and increased the level of AGP mRNA whereas alpha2M mRNA remained at the basal level. Inflammation in dexamethasone pretreated rats elicited changes which, in comparison to mRNA values for dexamethasone unpretreated inflamed rats, were seen as overexpression of alpha2M, full expression of AGP and incomplete expression of Hp, whereas Fb mRNA remained at the basal level. These data suggest that glucocorticoids are the principal inducers of alpha2M and AP-cytokines of Fb. For full induction of AGP, additive actions of glucocorticoids and AP-cytokines are required whereas expression of Hp is predominantly controlled by AP-cytokines.

Effect of oleoyl-estrone administration on corticosterone binding to tissues of lean and obese Zucker rats

A group of female Zucker lean and obese rats was treated with 3.5 micromol/day kg of oleoyl-estrone in liposomes (OE) injected i.v. continuously for 14 days with inserted osmotic minipumps. Samples of liver were extracted on days 0, 3, 6, 10 and 14 and the expression of corticosterone-binding globulin (CBG) was determined by Northern blot. On the same dates, the total binding capacity of plasma, liver, periovaric white adipose tissue (WAT) and subcutaneous WAT was also determined using tritium-labelled corticosterone. Treatment with OE resulted in diminished CBG gene expression in the liver, this being more marked in the obese rats. Basal (time 0) corticosterone binding was higher in the plasma, liver and WAT of lean rats. Treatment with OE resulted in a gradual and general loss of binding capacity in the plasma and all tissues studied, for lean and obese rats alike. Since CBG decreases may result in enhanced glucocorticoid availability (and effects), the global decrease in corticosterone binding observed can be interpreted as a counteractive response to the energy imbalance elicited by OE.

Characterization of an 88-kDa heat shock protein of Neurospora crassa that interacts with Hsp30

The small heat shock protein of Neurospora crassa, Hsp30, when employed in affinity chromatography, bound two cellular proteins that were identified as Hsp70 and Hsp88. Both Hsp70 and Hsp88 bound to Hsp30 in preference to other proteins, but binding of Hsp88 was more selective for Hsp30, and a direct interaction was observed. Transcripts for Hsp88, a newly characterized protein, are present at normal temperature, but they are strongly induced by heat shock. Its cDNA sequence predicts a protein with homology to mammalian Hsp110 family proteins, which are distantly related to Hsp70. Hsp88 and its homologues show greater similarity to Hsp70 in its N-terminal ATPase domain than in the C-terminal peptide-binding domain, and its ATP-binding motifs are conserved. Nevertheless, the N-terminal domain of Hsp88 (and related proteins) is consistently more hydrophobic and more basic than that of Hsp70 proteins. Within the C-terminal domain, the sequence corresponding to the DnaK alpha subdomain is conserved in the Hsp88/Hsp110 family proteins, whereas the DnaK beta subdomain sequence is not conserved. The interaction between Hsp70 and Hsp30 may reflect their cooperation as cochaperones for denatured proteins, whereas Hsp88 and Hsp30 may form a complex that interacts with potential substrates.

Sum1, a highly conserved WD-repeat protein, suppresses S-M checkpoint mutants and inhibits the osmotic stress cell cycle response in fission yeast

The S-M checkpoint ensures that entry into mitosis is dependent on completion of DNA replication. In the fission yeast Schizosaccharomyces pombe, the SM checkpoint mutant cdc2-3w is thought to be defective in receiving the checkpoint signal. To isolate genes that function in the checkpoint pathway, we screened an S. pombe cDNA library for genes that, when overexpressed, could suppress the checkpoint defect of cdc2-3w. Using this approach, we have identified a novel gene, sum1+ (suppressor of uncontrolled mitosis). sum1+ encodes a highly conserved WD-transducin repeat protein with striking sequence similarity to the human transforming growth factor (TGF)-beta-receptor interacting protein TRIP-1 and to the translation initiation factor 3 subunit eIF3-p39, encoded by the TIF34 gene in Saccharomyces cerevisiae. S. pombe sum1+ is an essential gene, required for normal cell growth and division. In addition to restoring checkpoint control, overexpression of sum1+ inhibits the normal cell cycle response to osmotic stress. Furthermore, we demonstrate that inactivation of the stress-activated MAP kinase pathway, required for cell cycle stress response, restores the S-M checkpoint in cdc2-3w cells. These results suggest that Suml interacts with the stress-activated MAP kinase pathway and raise the possibility that environmental conditions may influence the checkpoint response in fission yeast.

Cloning of a cyclic GMP phosphodiesterase gamma subunit from the ground squirrel retina

Recent evidence suggests that the two main classes of cones are not only equipped with different photopigments, but also exhibit differences in their downstream phototransduction cascade. An antibody against the gamma subunit of retinal cGMP phosphodiesterase (PDE) had previously been found to label all photoreceptors in the ground squirrel (Spermophilus tridecemlineatus). This property was utilized for the cloning of a cDNA fragment encoding the corresponding polypeptide. A lambda gt11 cDNA library was constructed and screened with the antibody. Positive clones were isolated, subcloned, and sequenced. Clones were used as probes in RNA blot hybridization, and the obtained sequence information was compared to other available gamma-PDE sequences. Four virtually identical cDNA clones were isolated. Both nucleic acid and amino acid sequence alignment placed this gene in the same group as bovine and human cone gamma-phosphodiesterase subunits. The predicted length of the translated protein was 84 amino acids, and its molecular weight 11 kD. The cDNA hybridized with an 0.6-kb transcript in retinal RNA from ground squirrel, Syrian golden hamster, and mouse, and also with a 1.4-kb transcript in the ground squirrel. We conclude that the isolated cDNA fragment encodes a gamma subunit of cone cGMP-PDE. This subunit is expressed in middle-wavelength sensitive cones (the predominant photoreceptor type in this species). It remains to be determined if this subunit is expressed in short-wavelength sensitive cones as well, or if these photoreceptors are equipped with another, unique gamma-PDE subunit.

RNA editing and alternative splicing generate mRNA transcript diversity from the Drosophila 4f-rnp locus

Extensive sequencing of genomic 4f-rnp and 15 cDNA clones isolated from libraries of 0-4-h embryos, pupae, and adult heads from Drosophila melanogaster has enabled identification of factors resulting in transcript sequence diversity. The 4f-rnp gene contains eight small introns. Among non-edited cDNAs, one transcript class potentially encodes a 943-amino-acid protein, within which several motifs are predicted, including a single C-terminal RNA-binding domain. Intron 5 is retained in all cDNAs examined except for a pupal cDNA, where it is excised. This potentially introduces an in-frame stop codon and predicts a truncated protein of 639 amino acids. One adult head transcript class is edited, some 31% of As being converted to Gs exclusive of edits within introns. An edit site in intron 4 changes a canonical 3'-terminal AG to GG, which interferes with splicing and is predicted to introduce a stop codon. A potential editing substrate recognition element in 4f-rnp contains the weak consensus sequence: 5'-G-G-G-N-A-A-G-3', which may interact with double-stranded RNA adenosine deaminase following pairing of 4f-rnp mRNA with an antisense transcript. It is possible that extensive editing in 4f-rnp destabilizes transcripts and thus provides a novel mechanism for post-transcriptional control of gene expression, although resolution of this point will require study of additional edited transcripts.

Molecular cloning, sequencing, and expression in Escherichia coli of mouse flavin-containing monooxygenase 3 (FMO3): comparison with the human isoform

The sequence of mouse flavin-containing monooxygenase 3 (FMO3) was obtained from several clones isolated from a mouse liver cDNA library. The nucleotide sequence of mouse FMO3 was 2020 bases in length containing 37 bases in the 5' flanking region, 1602 in the coding region, and 381 in the 3' flanking region. The derived protein sequence consisted of 534 amino acids including the putative flavin adenine dinucleotide and NADP+ pyrophosphate binding sites (characteristic of mammalian FMOs) starting at positions 9 and 191, respectively. The mouse FMO3 protein sequence was 79 and 82% identical to the human and rabbit FMO3 sequences, respectively. Mouse FMO3 was expressed in Escherichia coli and compared to E. coli expressed human FMO3. The FMO3 proteins migrated with the same mobility ( approximately 58 kDa) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The expressed FMO3 enzymes (mouse and human forms) were sensitive to heat and reacted in a similar manner toward metal ions and detergent. Catalytic activities of mouse and human FMO3 were high toward the substrate methimazole; however, in the presence of trimethylamine and thioacetamide, FMO-dependent methimazole oxidation by both enzymes was reduced by greater than 85%. Other substrates which inhibited methimazole oxidation were thiourea and thiobenzamide and to a lesser degree N,N-dimethylaniline. When probed with mouse FMO3 cDNA, FMO3 transcripts were detected in hepatic mRNA samples from female mice, but not in samples from males. FMO3 was detected in mRNA samples from male and female mouse lung, but FMO3 message was not detected in mouse kidney sample from either gender. Results of immunoblotting confirmed the tissue- and gender-dependent expression of mouse FMO3.

Photopigments and photoentrainment in the Syrian golden hamster

The Syrian golden hamster (Mesocricetus auratus) is an important model in the study of circadian rhythms. However, as in other mammals, little is known about the photoreceptors that mediate circadian entrainment. Using immunocytochemistry and RNA blot hybridization, we found no evidence for the presence of blue-/UV-sensitive opsin. In contrast, green-sensitive cone opsin was demonstrated in the retina both by immunocytochemistry and reverse-transcription PCR. When used as a probe in RNA blot hybridization, this PCR fragment labelled one transcript (5.8 kb) in hamster retinal RNA. These findings are in accordance with preliminary data from other investigators using electroretinography, which showed one cone-mediated photoreceptive mechanism with a maximum sensitivity of 501 nm, but none at shorter wavelengths. However, we found that non-saturating pulses of ultraviolet radiation (357 nm) caused phase shifts in locomotor behaviour. These results corroborate earlier reports that UV radiation can regulate the photoperiodic response in this animal. Having confirmed these apparently contradictory earlier reports, we discuss the mechanisms that might create a UV-triggered non-visual response in a green cone monochromat. Finally, we propose the use of the Syrian golden hamster as a model for photoreceptor development and function in the absence of S/UV cones.

Regulation of mouse liver flavin-containing monooxygenases 1 and 3 by sex steroids

Based on enzyme activity, protein levels, and mRNA levels, we have previously demonstrated the female-predominant, female-specific, and gender-independent expression in mouse liver of FMO forms 1, 3, and 5, respectively. This study investigated the roles of testosterone, 17 beta-estradiol, and progesterone in the regulation of hepatic FMOs. FMO expression was examined in gonadectomized CD-1 mice, normal CD-1 mice receiving hormonal implants, and gonadectomized mice receiving various hormonal treatments. Following castration of males, hepatic FMO activity levels were significantly increased and serum testosterone levels significantly decreased; however, administration of physiological levels of testosterone to castrated animals returned FMO activity and testosterone concentrations to control levels. When sexually intact and ovariectomized female mice were treated with testosterone, their hepatic FMO activity levels were reduced to those of their male counterparts, concomitant with high serum testosterone levels. In males, castration dramatically increased FMO3 and FMO1 expression, and testosterone replacement to castrated males resulted in ablation of FMO3 expression. In addition, testosterone administration to females (sexually intact and gonadectomized animals) reduced FMO1 expression and obviated FMO3 expression. In females, ovariectomy alone slightly reduced FMO activity, indicative of a possible stimulatory role of female sex steroids; however, female FMO isozyme expression was relatively unchanged, and hormone replacement therapy to ovariectomized females had no discernible effect. In males and females, FMO5 levels were unaffected by gonadectomy or hormone administration, thus indicating a sex hormone-independent mechanism of regulation for this isoform. Interestingly, FMO1 protein levels were increased in sexually intact males following treatment with 17 beta-estradiol; however, only a slight increase in FMO3 protein level was observed. No positive hormone effectors of female FMO expression were identified.

Spatial regulation of neuronal gene expression in response to nerve growth factor

To examine the cellular mechanisms whereby distally derived growth factors regulate nuclear responses in neurons, we have utilized compartmented cultures of sympathetic neurons to examine the regulation of two nerve growth factor (NGF)-inducible genes, tyrosine hydroxylase (TH) and p75 neurotrophin receptor (p75NTR). These studies demonstrate that NGF can signal retrogradely to mediate the induction of TH and p75NTR mRNAs. However, quantitative differences occurred as a function of the spatial localization of NGF exposure; application of NGF to cell bodies and proximal axons elicited peak levels of neuronal gene expression that were two- to threefold higher than when NGF was applied to distal axons alone. Furthermore, neurons responding maximally to NGF on distal axons were still able to respond to NGF administered to cell bodies and proximal axons. Biochemical analysis indicated that this difference in responsiveness was not due to differences in the number of TrkA/NGF receptors in the two compartments. Thus, although NGF signals retrogradely to mediate nuclear responses, the magnitude of these responses differs as a function of the spatial location of the activated NGF receptor:ligand complex. Moreover, these data suggest that neurons may be able to respond to a second cellular source of neurotrophins, even when target-derived neurotrophins are not limiting.

Alpha 1-tubulin mRNA level is increased during neurite outgrowth of NG 108-15 cells but not during neurite outgrowth inhibition by CNS myelin

alpha 1-tubulin is an isotype of alpha-tubulin, and its mRNA is expressed in the rodent nervous system. A high level of alpha 1-tubulin mRNA in neurones is associated with axonal outgrowth during development as well as with axonal regeneration after axotomy in adult animals. We quantitated alpha 1-tubulin mRNA levels in motor neurone-like NG 108-15 cells using Northern blots in order to determine whether the expression of this neurite outgrowth-associated gene is regulated in NG 108-15 cells during neurite extension and during inhibition of this process by CNS myelin. Here we report that during the acute phase of neurite outgrowth, alpha 1-tubulin mRNA level increases in NG 108-15, a maximal induction of 1.7-fold over the initial level occurring 24 h after neurite outgrowth onset. By contrast, when these cells are plated on CNS myelin alpha 1-tubulin mRNA levels show no such increase. These findings indicate that an increase of the alpha 1-tubulin mRNA level is associated with neurite outgrowth of NG 108-15 cells. More interestingly, this study also demonstrates that the inhibition of neurite outgrowth by CNS myelin may affect the expression of a gene encoding a protein involved in neurite extension.

Glucocorticoids induce corticosteroid-binding globulin biosynthesis by immature mouse liver and kidney

Marked changes in mouse corticosteroid-binding globulin (CBG) gene expression in the liver and kidney occur postnatally. To study the influence of glucocorticoids on the initiation of mouse CBG biosynthesis in these tissues during the first two weeks after birth, we administered dexamethasone (0.5 microgram/g body wt/day) to 4- and 11-day-old pups for three days. This resulted in higher serum CBG and hepatic CBG mRNA levels in animals, irrespective of their ages. Higher relative amounts of CBG mRNA in the kidneys of 14-day-old pups after three days of dexamethasone treatment co-incided with higher amounts of intact and proteolytically cleaved CGB in their urine, and both are indicative of increased CGB production by the developing renal tubules. When an additional group of 11-day-old pups (n = 4) was treated with 0.25 microgram dexamethasone/g body weight per day for five days, this also resulted in significantly higher levels of serum CBG (P < 0.01), hepatic CBG mRNA (P < 0.01) and renal CBG mRNA (P < 0.05), compared to littermates treated with the oil vehicle alone. In contrast, serum CBG levels progressively decreased in adult female mice during five days of treatment with 0.5 microgram dexamethasone/g body weight per day. Taken together, these data indicate that glucocorticoids induce murine CBG gene expression in the immature liver and kidney, and support the concept that the effects of glucocorticoids on CBG gene expression are developmentally stage-specific.

IMP dehydrogenase from Pneumocystis carinii as a potential drug target

Mycophenolic acid, a specific inhibitor of IMP dehydrogenase (IMPDH; EC 1.1.1.205), is a potent inhibitor of Pneumocystis carinii growth in culture, suggesting that IMPDH may be a sensitive target for chemotherapy in this organism. The IMPDH gene was cloned as a first step to characterizing the enzyme and developing selective inhibitors. A 1.3-kb fragment containing a portion of the P. carinii IMPDH gene was amplified by PCR with two degenerate oligonucleotides based on conserved sequences in IMPDH from humans and four different microorganisms. Northern hybridization analysis showed the P. carinii IMPDH mRNA to be approximately 1.6 kb. The entire cDNA encoding P. carinii IMPDH was isolated and cloned. The deduced amino acid sequence of P. carinii IMPDH shared homology with bacterial (31 to 38%), protozoal (48 to 59%), mammalian (60 to 62%), and fungal (62%) IMPDH enzymes. The IMPDH cDNA was expressed by using a T7 expression system in an IMPDH-deficient strain of Escherichia coli (strain S phi 1101). E. coli S phi 1101 cells containing the P. carinii IMPDH gene were able to grow on medium lacking guanine, implying that the protein expressed in vivo was functional. Extracts of these E. coli cells contained IMPDH activity that had an apparent Km for IMP of 21.7 +/- 0.3 microM and an apparent Km for NAD of 314 +/- 84 microM (mean +/- standard error of the mean; n = 3), and the activity was inhibited by mycophenolic acid (50% inhibitory concentration, 24 microM; n = 2).

The gamma subfamily of DNA polymerases: cloning of a developmentally regulated cDNA encoding Xenopus laevis mitochondrial DNA polymerase gamma

We used the known sequence of the Saccharomyces cerevisiae DNA polymerase gamma to clone the genes or cDNAs encoding this enzyme in two other yeasts, Pychia pastoris and Schizosaccharomyces pombe, and one higher eukaryote, Xenopus laevis. To confirm the identity of the final X.laevis clone, two antisera raised against peptide sequences were shown to react with DNA polymerase gamma purified from X.laevis oocyte mitochondria. A developmentally regulated 4.6 kb mRNA is recognized on Northern blots of oocyte RNA using the X.laevis cDNA. Comparison of the four DNA polymerase gamma gene sequences revealed several highly conserved sequence blocks, comprising an N-terminal 3'-->5'exonuclease domain and a C-terminal polymerase active center interspersed with gamma-specific gene sequences. The consensus sequences for the DNA polymerase gamma exonuclease and polymerase domains show extensive sequence similarity to DNA polymerase I from Escherichia coli. Sequence conservation is greatest for residues located near the active centers of the exo and pol domains of the E.coli DNA polymerase I structure. The domain separating the exonuclease and polymerase active sites is larger in DNA polymerase gamma than in other members of family A (DNA polymerase I-like) polymerases. The S.cerevisiae DNA polymerase gamma is atypical in that it includes a 240 residue C-terminal extension that is not found in the other members of the DNA polymerase gamma family, or in other family A DNA polymerases.

Pancreatic adenocarcinoma cell line, MDAPanc-28, with features of both acinar and ductal cells

CONCLUSION

We established a new human pancreatic adenocarcinoma cell line, MDAPanc-28. Studies on this new line indicate that it expressed both acinar and ductal gene products suggesting that the patterns of gene expression in the pancreatic adenocarcinoma from which this cell line arose have features similar to those of the protodifferentiated cells hypothesized by Rutter and his colleagues for the developing pancreas (1,2).

BACKGROUND

The cell line arose from a tumor that, like most pancreatic adenocarcinomas, was ductal on the basis of its histological appearance.

METHODS

Once the cell line was established in culture, they were subjected to cytogenetic analysis and tested for their ability to grow in nude mice. RNA from the cells was analyzed by Northern blot analysis and PCR of reverse transcribed cDNA for the expression of both acinar and duct cell gene products. DNA was analyzed for the presence of mutated K-ras at codon 12.

RESULTS

The cell line expressed trypsin and ribonuclease RNA, which are considered to be acinar cell markers, and carbonic anhydrase II (CAII), which is considered to be a duct-cell markers. The histological appearance of xenografts in nude mice was similar to that of the tumor from which the cell line was established. The chromosome number varied between 46 and 60.

Molecular cloning and characterization of a gibberellin-inducible, putative alpha-glucosidase gene from barley

A putative alpha-glucosidase clone has been isolated from a cDNA library constructed from mRNA of barley aleurones treated with gibberellin A 3 (GA). The clone is 2752 bp in length and has an uninterrupted open reading frame encoding a polypeptide of 877 amino acids. A 680 amino acid region is 43% identical to human lysosomal alpha-glucosidase and other glycosyl hydrolases. In isolated aleurones, the levels of the corresponding mRNA increase strongly after the application of GA, similar to the pattern exhibited by low-pI alpha-amylase mRNA. High levels are also observed in the aleurone and scutellum after germination, while low levels are found in developing seeds. The genome contains a single form of this alpha-glucosidase gene and two additional sequences that may be related genes or pseudogenes.

Glycine reductase of Clostridium litorale. Cloning, sequencing, and molecular analysis of the grdAB operon that contains two in-frame TGA codons for selenium incorporation

A 2.8-kb HindIII fragment, containing three open reading frames, has been cloned and sequenced from Clostridium litorale. The first gene grdA encoded the selenocysteine-containing protein PA of the glycine reductase complex, a protein of 159 amino acids with a deduced molecular mass of 16.7 kDa. The second gene (grdB) encoded the 47-kDa subunit of the substrate-specific selenoprotein PB glycine that is composed of 437 amino acids. The third gene contained the 5'-region of the gene for thioredoxin reductase, trxB. All gene products shared high similarity with the corresponding proteins from Eubacterium acidaminophilum. In both genes grdA and grdB, the opal termination codon (TGA) was found inframe, indicating the presence of selenocysteine in both polypeptides. Northern-blot analysis showed that grdA and grdB are organized as one operon. Unlike Escherichia coli, no stable secondary structures of the corresponding mRNA were found immediately downstream of the UGA codons to direct an insertion of selenocysteine into the grdA and grdB transcripts of C. litorale. Instead, a secondary structure was identified in the 3'-untranslated region of grdB.