Complete nucleotide sequence of the messenger RNA coding for chicken muscle glyceraldehyde-3-phosphate dehydrogenase

Two glutamate decarboxylase forms corresponding to the mammalian GAD65 and GAD67 are expressed during development of the chick telencephalon

The gamma-aminobutyric acid (GABA)-synthesizing enzyme glutamate decarboxylase (GAD) was studied during development of the chick telencephalon. By means of reverse-phase HPLC analysis, we showed that GABA indeed accumulates during embryogenesis, whereas the levels of glutamate, the substrate for GAD, are more or less unchanged up to later developmental stages. The enzyme activity increased approximately 25-fold from embryonic day 3 to embryonic day 17. Immunoblotting data revealed that two GAD proteins, of approximately 65 and 67 kDa, were present during the period investigated. Furthermore, Northern blot analysis with probes obtained from rat cDNA sequences, as well as a chicken-specific probe for GAD65 generated by means of reverse transcriptase-polymerase chain reaction (RT-PCR), strengthened the interpretation that the chick embryo expresses genes corresponding to GAD65 and GAD67. The rat probes recognized transcript sizes of 3.9 kb (GAD65) and 5.6 kb (GAD67), sizes which are different from those of the rat brain (Erlander et al., Neuron, 7, 91-100, 1991). Sequencing of the RT-PCR products revealed a high level of homology (82% at the nucleotide level) between the mammalian and chick GAD65 genes. Taken together, these findings suggest that the chick embryo expresses two GAD genes during embryogenesis. The functional properties of each gene product remain to be investigated.

Chicken guanylate-binding protein. Conservation of GTPase activity and induction by cytokines

To gain further insights into the cytokine network of birds, we used polymerase chain reaction technology to clone a cDNA that codes for a chicken homolog of the interferon-induced guanylate-binding proteins (GBPs). In its N-terminal moiety, the 64-kDa chicken GBP contains two sequence blocks of 100 and 19 amino acids, respectively, that are about 70% identical to mammalian GBPs. The first region includes two motifs of the canonical GTP-binding consensus element. The other parts of chicken GBP are poorly conserved, except for a CAAX motif at the extreme C terminus which might signal isoprenylation. Like mammalian GBPs, recombinant chicken GBP specifically bound to agarose-immobilized guanine nucleotides and hydrolyzed GTP to both GDP and GMP. Regulation by interferons was also conserved: chicken GBP RNA was barely detectable in uninduced chicken cells. Low GBP RNA levels were found in cells treated with type I interferon, whereas very high levels were observed in cells treated with supernatant of a chicken T cell line that secretes a gamma-interferon-like activity. Together with recent phylogenetic studies of interferon genes, these results suggest that in spite of low sequence conservation, the various components of the avian interferon system are functionally well conserved.

Cellular distribution and regulation of NHE-1 isoform of the NA-H exchanger in the avian osteoclast

The sodium-hydrogen exchanger (NHE) has been implicated in bone resorption by osteoclasts. We have studied expression of NHE-1, an isoform of the NHE, in chicken bone marrow mononuclear phagocyte precursors during differentiation into the osteoclast phenotype in culture. A monoclonal anti-body raised against the carboxy-terminus of NHE-1 detected the presence of a 100 kDa protein (similar to the mammalian form of NHE-1) in the osteoclasts. Laser scanning confocal microscopy revealed association with the alpha(v)beta(3) integrin and focal adhesion kinase (pp(125)FAK) at the basolateral membrane (BLM) of the osteoclast in addition to a more generalized cellular distribution. A fragment of avian NHE-1 cDNA was obtained by polymerase chain reaction cloning, and it was used to characterize expression of NHE-1 transcripts in cultured chicken osteoclast precursors. The avian NHE-1 message was a 3.9 kB band on Northern analysis, which differed from the mammalian message. Retinoic acid (RA) elicited an increase in the steady-state intracellular pH (pH(1)) from 6.87 to 7.10 in the absence of bicarbonate and was inhibited by ethylisopropylamiloride, an inhibitor of Na-H exchange. Using ribonuclease protection assays, we found that NHE-1 transcripts are induced as cells differentiate in vitro and in response to 13-cis-RA. Western blot analysis indicated that protein levels also increased in response to 13-cis-RA. Our results demonstrate expression of NHE-1 in avian osteoclasts with a complex cellular distribution in culture, and NHE-1 expression is induced as cells differentiate into mature osteoclasts in response to 13-cis-RA.

Expression of neurotrophins and trk receptors in the avian retina

Using the RNase protection assay, we have found that nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are expressed in the avian retina during development. The expression peaks around embryonic days 12-15, with decreasing levels at later stages of development. Abundant levels of NGF and BDNF but low levels of NT-3 mRNA were found in the adult retina. We also found that light/darkness regulated the levels of NGF and BDNF mRNAs but not the levels of NT-3 mRNA in the 5-day-old chicken retina. It was demonstrated that NGF and BDNF mRNA levels were up-regulated by light exposure. The cellular localization of mRNA expression for the neurotrophins and neurotrophin receptors TrkA, TrkB, and TrkC in the retina was studied using in situ hybridization. The patterns of NGF and trkA mRNA expression were very similar and were localized to the external part of the inner nuclear layer on the border with the outer plexiform layer and corresponded to the localization of horizontal cells. NT-3 labeling was also found over the external part of the inner nuclear layer, whereas trkC mRNA was found over all layers in the retina. BDNF labeling was found over all layers in the retina, whereas TrkB labeling was intense over cells in the ganglion cell layer, which is in agreement with the response of ganglion cells to BDNF stimulation. Functional neurotrophin receptors were suggested by the response of retinal explants to neurotrophin stimulation. These data indicate that the neurotrophins play local roles in the retina that involve interactions between specific neuronal populations, which were identified by the localization of the Trk receptor expression. The data also suggest that NGF and BDNF expression is regulated by normal neuron usage in the retina.

All-trans retinoic acid stimulates and maintains neurite outgrowth in nerve growth factor-supported developing chick embryonic sympathetic neurons

In explanted embryonic chick sympathetic neurons, all-trans retinoic acid (RA) as well as nerve growth factor (NGF) were found to be required for neuronal survival and neurite outgrowth at early stages of development (day 6.5-7) in agreement with previous work (Rodriguez-Tébar and Rohrer [1991] Development 112:813-820). The dependence of neurons on all-trans RA for survival diminished at later stages of development. However, all-trans RA was found to be needed at all stages of development in order to maximize neurite outgrowth. Further, removal of all-trans RA from the cultures led to a rapid degeneration of the formed neurites, demonstrating the essentiality of all-trans RA for both the development of neurites, and for the maintenance of existing neurites in cultured embryonic sympathetic neurons. The mechanism whereby all-trans RA exerts its effects on embryonic sympathetic neurons may involve activation of the nuclear retinoic acid and retinoid-X receptor (RAR and RXR) families. The results of Northern blot analyses and/or reverse transcriptase-polymerase chain reaction (RT-PCR) studies show that embryonic sympathetic ganglia express RAR beta, RAR gamma and RXR gamma mRNAs. RXR gamma mRNA is expressed at highest levels in immature neurons that are not yet responsive to NGF (day 6.5-7) and message levels decline with increasing developmental age. In contrast, RAR beta transcript levels are barely detectable at day 6.5-7, and increase approximately 4-fold in ganglia from embryos at day 8.5-9 and decline thereafter. RT-PCR studies show that RAR gamma mRNA is expressed both early (day 6.5-7) and late (day 15) in ganglionic development. Transcripts for the NGF receptors, p75NGFR and p140trk were also examined. The appearance of a single 2.7 kb p140trk transcript coincides with the time when RAR beta mRNA is maximally expressed, raising the possibility that NGF receptors may be targets of retinoid action. Evidence is also presented that all-trans RA may enhance neurite outgrowth by mechanisms other than simply inducing NGF-responsiveness of neurons.

Induction of avian cardiac myogenesis by anterior endoderm

An experimental system was devised to study the mechanisms by which cells become committed to the cardiac myocyte lineage during avian development. Chick tissues from outside the fate map of the heart (in the posterior primitive streak (PPS) of a Hamburger & Hamilton stage 4 embryo) were combined with potential inducing tissues from quail embryos and cultured in vitro. Species-specific RT-PCR was employed to detect the appearance of the cardiac muscle markers chick Nkx-2.5 (cNkx-2.5), cardiac troponin C and ventricular myosin heavy chain in the chick responder tissues. Using this procedure, we found that stage 4–5 anterior lateral (AL) endoderm and anterior central (AC) mesendoderm, but not AL mesoderm or posterior lateral mesendoderm, induced cells of the PPS to differentiate as cardiac myocytes. Induction of cardiogenesis was accompanied by a marked decrease in the expression of rho-globin, implying that PPS cells were being induced by anterior endoderm to become cardiac myocytes instead of blood-forming tissue. These results suggest that anterior endoderm contains signaling molecules that can induce cardiac myocyte specification of early primitive streak cells. One of the cardiac muscle markers induced by anterior endoderm, cNkx-2.5, is here described for the first time. cNkx-2.5 is a chick homeobox-containing gene that shares extensive sequence similarity with the Drosophila gene tinman, which is required for Drosophila heart formation. The mesodermal component of cNkx-2.5 expression from stage 5 onward, as determined by in situ hybridization, is strikingly in accord with the fate map of the avian heart. By the time the myocardium and endocardium form distinct layers, cNkx-2.5 is found only in the myocardium. cNkx-2.5 thus appears to be the earliest described marker of avian mesoderm fated to give rise to cardiac muscle.

Collagen fibrillogenesis in situ: fibril segments undergo post-depositional modifications resulting in linear and lateral growth during matrix development

Elucidating how collagen fibril growth is regulated is important in determining how tissues are assembled. Fibrils are deposited as segments. The growth of these segments is an important determinant of tissue architecture, stability, and mechanical attributes. Fibril segments were isolated from developing tendons and their structure characterized. The post-depositional changes leading to linear and lateral growth of fibrils also were examined. Segments extracted from 14-day chicken embryo tendons had a mean length of 29 microns. The segments were asymmetric, having a short and a long tapered end. Most of the segments were centrosymmetric with respect to molecular packing. Segments extracted from 12- to 16-day tendons had the same structure, but mean segment length increased incrementally due to the addition of an increasingly large population of longer segments. At 17 days of development there was a precipitous increase in segment length. The morphological data indicate that the increase in length was the result of lateral associations among adjacent segments. Analysis demonstrated that this fibril growth was associated with a significant decrease in fibril associated decorin. Using immunoelectron microscopy, decorin was seen to decrease significantly at 18 days of development. When decorin content was biochemically determined, a decrease also was observed. Decorin mRNA also decreased relative to fibrillar collagen mRNA during the same period. These data support the hypothesis that a decrease in fibril-associated decorin is necessary for fibril growth associated with tissue maturation. Growth through post-depositional fusion allows for appositional and intercalary growth and would be essential for normal development, growth, and repair.

Analysis of AP-1 function in cellular transformation pathways

To understand the role of endogenous AP-1 activity in cellular transformation induced by oncogenes, we have made use of a fos mutant (supfos-1) and a jun mutant (supjun-1), either of which can function as a transdominant inhibitor of AP-1-mediated transcriptional regulation. Chicken embryo fibroblasts (CEF) infected with a series of transforming retroviruses were doubly infected with retrovirus carrying supfos-1 or supjun-1, and suppression of cellular transformation was monitored in terms of reversion to normal cellular morphology or acquisition of anchorage-dependent growth. Cellular transformation induced by several exogenously expressed transforming genes of the fos or jun family was efficiently suppressed, as expected. CEF transformed by v-src, v-yes, v-fps, c-Ha-ras, and N-terminally truncated c-raf were also induced to revert to the normal phenotype by these transdominant mutants, suggesting that functional transcription factor AP-1 activity is essential for the cellular transformation induced by these oncogenes. The suppression is not attributable to nonspecific inhibition of cellular proliferation, because CEF transformed by v-ros or v-myc were not induced to revert to the normal phenotype. We next analyzed changes in all known components of chicken AP-1 induced by v-src, c-Ha-ras, or activated c-raf transformation. The levels of both Fra-2 and c-Jun expression were elevated two- to fourfold, and hyperphosphorylation of Fra-2 was also observed. We further showed that Fra-2-c-Jun heterodimer is mainly responsible for the elevated AP-1 DNA-binding activity in these transformed cells, and we propose that this heterodimer play a crucial role in the transformation induced by these oncogenes.

Sequence and expression of a glyceraldehyde-3-phosphate dehydrogenase-encoding gene from quail embryo fibroblasts

Using differential hybridization techniques, a cDNA library derived from a line of v-myc-transformed quail embryo fibroblasts was screened for clones whose expression was elevated in transformed, as compared with normal, cells. One of the isolated clones contained the entire coding region of the quail glyceraldehyde-3-phosphate dehydrogenase-encoding gene (GAPDH). A comparison of the deduced 333-amino-acid (aa) sequence of quail GAPDH with that of the only other avian (chicken) GAPDH sequence known, and with those of mammalian counterparts indicates the strong aa sequence conservation of this glycolytic enzyme. GAPDH is expressed in all transformed and non-transformed quail and chicken embryo fibroblasts and macrophages tested, with a moderate elevation of expression in most of the transformed cell lines. In the avian genomes, GAPDH is present in a single copy, in contrast to the high number of GAPDH-related sequences in mammalian species.

Nucleotide sequence and molecular evolution of the gene coding for glyceraldehyde-3-phosphate dehydrogenase in the thermoacidophilic archaebacterium Sulfolobus solfataricus

A Sulfolobus solfataricus genomic library cloned in the EMBL3 phage was screened using as probes synthetic oligonucleotides designed from the known amino acid sequence of a peptide obtained from the purified glyceraldehyde-3-phosphate dehydrogenase (aGAPD) protein. The screening led to the isolation of six recombinant phages (lambda G1-lambda G6) and one of them (lambda G4) contained the entire GAPD gene. The deduced amino acid sequence accounts for a protein made of 341 amino acids and the initial methionine is encoded by a GTG triplet. Alignment of the S. solfataricus aGAPD sequence versus GAPD from archaea, eukarya, and bacteria showed that aGAPD is very similar to other archaebacterial but not to eukaryotic or eubacterial GAPD. For known archaebacterial GAPD sequences, the rate of nucleotide substitutions per site per year showed that these sequences are homologous not only at the amino acid but also at the nucleotide level. The evolutionary rates are nearly similar to those reported for other eukaryotic genes.

Control of plasminogen-activator inhibitor type 2 gene expression in the differentiation of monocytic cells

Plasminogen-activator inhibitor type 2 (PAI-2) is a potent and primary inhibitor of urokinase-type plasminogen activator. Its production in monocytic cells is thought to play an important role in the control of localized proteolysis at sites of invasion as occurs in the control of inflammatory processes, tumor invasion and cellular differentiation. Therefore, we have investigated the mechanisms responsible for the regulation of PAI-2 gene expression in differentiating monocytic cells using the human promyelocytic cell line, HL-60, as a model. These cells are induced to differentiate to a macrophage-like phenotype in response to phorbol ester [4-phorbol-12-myristate 13-acetate (PMA)]. The levels of PAI-2 mRNA are barely detectable in undifferentiated cells, however, activation with PMA is associated with a rapid induction of PAI-2 transcripts, reaching a maximum of 25-fold in 4 h. Nuclear run on assays demonstrate that this induction is related primarily to an enhanced rate of gene transcription. Inhibition of de novo protein synthesis by cycloheximide increases PAI-2 mRNA levels in both resting (sevenfold) and PMA-treated cells (fivefold) after 4 h, but has no detectable effect on the rate of PAI-2 gene transcription. The initial apparent half-life of the induced PAI-2 mRNA, determined by actinomycin-D-decay experiments, is very short, 32 min, suggesting rapid turnover. Furthermore, the PAI-2 mRNA transcript is stabilized in the presence of cycloheximide, with a fourfold increase in the observed half-life. The results demonstrate that PAI-2 gene expression is regulated through post-transcriptional mechanisms in undifferentiated cells, while both transcriptional and post-transcriptional events govern the level of PAI-2 transcripts in cells differentiated along the monocytic pathway. Destabilization of the PAI-2 transcript may be associated with (A + U)-rich sequences found in the 3'-untranslated region of PAI-2 mRNA. The short half life and rapid, strong induction of PAI-2 point to an important, perhaps crucial, role in the differentiation of monocyte cells.

Immunoglobulin production stimulating factor-II? (IPSF-II?) is glyceraldehyde-3-phosphate dehydrogenase like protein

Amino acid sequence of the 36 KD protein which is the active subunit of immunoglobulin production stimulating factor-II alpha (IPSF-II alpha) derived from Burkitt's lymphoma Namalwa cells was analyzed for the 20 amino acids from N-terminus. The N-terminal amino acid sequence of this protein coincided very closely with glyceraldehyde-3-phosphate dehydrogenase (GPD; EC 1.2.1.12) derived from various origins. Especially, it was completely homologous with that of human liver GPD. Several GPD's derived from human erythrocyte, rabbit muscle and Bacillus stearothermophilus also stimulated IgM production of hybridomas, as well as IPSF-II alpha. Conversely, IPSF-II alpha had GPD enzymic activity as strong as rabbit muscle and B. stearothermophilus, and stronger than human erythrocyte GPD. These results suggested that 36 KD subunit of IPSF-II alpha was a GPD, or GPD like protein. The level of mRNA for IgM was not enhanced by IPSF-II alpha in hybridoma cells, though the IgM productivity of the cell was remarkably stimulated by the protein, indicating that IPSF-II alpha does not stimulate immunoglobulin production by enhancement of transcription.

Isolation and characterization of a Ustilago maydis glyceraldehyde-3-phosphate dehydrogenase-encoding gene

The complete nucleotide sequence of the glyceraldehyde-3-phosphate dehydrogenase gene from the corn smut fungus Ustilago maydis is reported. The gene encodes a 337-amino acid protein, parts of which show sequence identity to corresponding regions of GAPDH-encoding genes from other organisms. A single, putative 407-bp intron interrupts the tenth codon. Codon usage is highly biased for codons ending in cytosine.

Use of an RNA folding algorithm to choose regions for amplification by the polymerase chain reaction

We have used the program FOLD, which employs the Zuker folding algorithm, to identify regions of stable secondary structure in three chicken proto-oncogene mRNAs: c-src, c-myc, and c-fos. We have found that use of reverse transcriptase to synthesize a cDNA template for amplification by the polymerase chain reaction is successful only if the region chosen for amplification does not contain stem structures with calculated free energies less than -14 kcal/mol.

The muridae glyceraldehyde-3-phosphate dehydrogenase family

Although only one gene is known to be functional, numerous glyceraldehyde-3-phosphate dehydrogenase (GAPDH) related sequences are scattered throughout Mus musculus and Rattus rattus genomes. In this report we show that: (1) GAPDH pseudogenes are repeated to comparable extents, at least 400 copies, in 12 other Muridae species; (2) the complete, or nearly so, sequence of GAPDH messenger RNA is amplified, and a high proportion, if not all of these copies, are intronless; (3) GAPDH pseudogenes are preferentially located in heavily methylated and DNAse I-insensitive regions of chromatin; and (4) the presence of atypical GAPDH-related mRNAs in different cellular contexts raises the possibility that more than one GAPDH gene is transcribed.

Human glyceraldehyde-3-phosphate dehydrogenase pseudogenes: molecular evolution and a possible mechanism for amplification

We screened two human genomic libraries and isolated 14 different clones, designated lambda G1 and EG1-EG13, homologous to human glyceraldehyde-3-phosphate dehydrogenase (GAPD) cDNA. Subcloning and sequencing these recombinant phages led us to classify them as five different pseudogenes (psi G1-psi G5). All these sequences show such features typical of processed pseudogenes as numerous mutations, insertions, and deletions. The identity of numerous mutated sites among these pseudogenes and the presence of two Alu sequences flanking both ends of psi G1 suggest that GAPD pseudogenes originated from a unique reverse transcribed mRNA followed by gene duplication. The rate of nucleotide substitutions per site per year for known GAPD functional genes is low both for the synonymous substitutions (1.87 x 10(-9] and for the nonsynonymous substitutions (0.12 x 10(-9] and indicates that the GAPD cDNA sequence is well conserved not only at the amino acid level, but also at the nucleotide level. The rate of nucleotide substitutions per site per year for GAPD pseudogenes shows a higher value (5.9 x 10(-9] and suggests that these pseudogenes do not have any functional role.

4-Chloroacetylpyridine adenine dinucleotide. A highly reactive and chromophoric affinity label of glyceraldehyde-3-phosphate dehydrogenase from sturgeon

The analogue of NAD+, 4-chloroacetylpyridine-adenine dinucleotide (clac4PdAD+), inactivated the glyceraldehyde-3-phosphate dehydrogenase from sturgeon at a high rate. An affinity labeling was shown to occur with clac4PdAD+. The mononucleotide 4-chloroacetylpyridine 1-beta-D-ribose 5'-phosphate (clac4PdMN+) reacted with the enzyme in a second-order reaction whose rate was much smaller than that calculated for clac4PdAD+ taken as a second-order rate reagent. The rate of the reaction of clac4PdAD+ with the enzyme was determined by stopped flow, using as a probe the long-wavelength absorption maximum (430 nm) formed concomitantly with inactivation of the enzyme. Computer-assisted graphic simulation showed that the clac4PdAD+ analogue could bind to the active site of the enzyme from Bacillus stearothermophilus in a similar manner to that of NAD+, and that the reactive carbon and the reactive thiolate of Cys-149 were within bonding distance. The absorption at 430 nm was linearly proportional to the substoichiometric concentration of clac4PdAD+/mole subunit. Thiol titration suggested the modification of one thiol residue per subunit. The modified thiol was identified by degradation as Cys-149. In contrast to the absorption band generated during the reaction of the 3-chloroacetylpyridine-adenine dinucleotide (clac3PdAD+) with the same enzyme [Eur. J. Biochem. (1982) 127, 519-524; 129, 437-446], enzyme inactivated with clac4PdAD+ and clac4PdMN+ exhibited an absorption maximum at long wavelength which was still present after denaturation. The chromophore is proposed to be the enol form of the alpha-thioether ketone produced by alkylation of the thiolate of Cys-149 by the chloroacetyl group.

A role for glyceraldehyde-3-phosphate dehydrogenase in the development of thermotolerance in Xenopus laevis embryos

During heat shock, Xenopus laevis embryos exhibit an increase in the rate of accumulation of lactate and a loss of ATP relative to non-heat-shocked control embryos. These results suggest that heat shock stimulates a shift in energy metabolism to anaerobic glycolysis while at the same time causing an increase in the demand for ATP. We have evidence indicating that the embryo may meet such demands placed on it by increasing the levels of some glycolytic enzymes. In this report, we show that heat shock stimulates increases in the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase [( EC 1.2.1.12] GAPDH). The specific activity of GAPDH shows a significant increase after heat shock, which correlates with the accumulation of GAPDH in heat-shocked embryos as detected by immunoblotting. Increases in GAPDH-specific activity are variable, however, and are inversely proportional to the levels of specific activity in control embryos; i.e., constitutive enzyme activity. We further analyzed the heat-enhanced accumulation of GAPDH by electrophoretically separating GAPDH isozymes on nondenaturing polyacrylamide gels. Control embryos exhibit a single isozyme of GAPDH, whereas heat-shocked embryos exhibit two isozymes of GAPDH. When these isozymes are labeled with [35S]methionine, separated by nondenaturing gel electrophoresis, and analyzed by fluorography, a heat-shock protein is found to comigrate with the isozyme unique to the heat-shocked sample. Enzyme activity assays at different temperatures suggest that this isozyme has optimum enzymatic activity only at heat-shock temperatures. We have correlated a 35-kD heat-shock protein (hsp35) with GAPDH using the following evidence: this hsp comigrates with GAPDH on one-dimensional SDS polyacrylamide gels; heat-enhanced increases in GAPDH specific activity correlate with hsp35 synthesis; and hsp35 and GAPDH have similar peptide maps. This relationship also provides a compelling explanation for the restriction of hsp35 synthesis to the vegetal hemisphere cells of heat-shocked early gastrulae reported previously (Nickells, R. W., and L. W. Browder. 1985. Dev. Biol. 112:391-395).

Glucocorticoids selectively inhibit translation of ribosomal protein mRNAs in P1798 lymphosarcoma cells

When P1798 murine lymphosarcoma cells are exposed to 10(-7) M dexamethasone, there is a dramatic inhibition of rRNA synthesis, which is completely reversible when the hormone is withdrawn. In the present experiments we examined whether dexamethasone treatment causes any alteration in the accumulation or utilization of mRNAs that encode ribosomal proteins (rp mRNAs). No effect on the accumulation of six different rp mRNAs was detected. However, the translation of five of six rp mRNAs was selectively inhibited in the presence of the hormone, as judged by a substantial decrease in ribosomal loading. Normal translation of rp mRNA was resumed within a few hours after hormone withdrawal. In untreated or fully recovered cells, the distribution of rp mRNAs between polyribosomes and free ribonucleoprotein is distinctly bimodal, suggesting that rp mRNAs are subject to a particular form of translational control in which they are either translationally inactive or fully loaded with ribosomes. A possible relationship between this mode of translational control and the selective suppression of rp mRNA translation by glucocorticoids is discussed.

Glucocorticoids selectively inhibit translation of ribosomal protein mRNAs in P1798 lymphosarcoma cells

When P1798 murine lymphosarcoma cells are exposed to 10(-7) M dexamethasone, there is a dramatic inhibition of rRNA synthesis, which is completely reversible when the hormone is withdrawn. In the present experiments we examined whether dexamethasone treatment causes any alteration in the accumulation or utilization of mRNAs that encode ribosomal proteins (rp mRNAs). No effect on the accumulation of six different rp mRNAs was detected. However, the translation of five of six rp mRNAs was selectively inhibited in the presence of the hormone, as judged by a substantial decrease in ribosomal loading. Normal translation of rp mRNA was resumed within a few hours after hormone withdrawal. In untreated or fully recovered cells, the distribution of rp mRNAs between polyribosomes and free ribonucleoprotein is distinctly bimodal, suggesting that rp mRNAs are subject to a particular form of translational control in which they are either translationally inactive or fully loaded with ribosomes. A possible relationship between this mode of translational control and the selective suppression of rp mRNA translation by glucocorticoids is discussed.

The glyceraldehyde-3-phosphate dehydrogenase gene family in the nematode, Caenorhabditis elegans: isolation and characterization of one of the genes

The isolation and genomic sequence of one of possibly four glyceraldehyde-3-phosphate dehydrogenase genes in the nematode, Caenorhabditis elegans is presented. The complete nucleotide sequence of the coding as well as the noncoding flanking regions of this gene has been determined. The deduced amino-acid sequence agrees with the sequence of typical glyceraldehyde-3-phosphate dehydrogenase enzymes and its molecular weight of 36,235 agrees with its size determined previously (Yarbrough, P. and Hecht, R. (1984) J. Biol. Chem. 259, 14711-14720). That this isolated gene encodes a nematode glyceraldehyde-3-phosphate dehydrogenase is additionally confirmed by demonstrating its immunoreactivity to an anti-nematode glyceraldehyde-3-phosphate dehydrogenase antibody after its expression as a fusion protein with dihydrofolate reductase. Codon utilization follows a pattern typical of other expressed nematode genes. The gene is split by two introns that are highly conserved in comparison to other introns observed in C. elegans. The placement of one of these introns is conserved with respect to the chicken glyceraldehyde-3-phosphate dehydrogenase gene. Within the 5' flanking sequence homology to actin and the homology 2 block of the major myosin gene (unc-54) is noted. It is of interest that the 3' flanking region contains a CAAAT box, followed by a TATAAT box, before an open reading frame of a closely linked gene that also contains a small AT-rich intron with the nematode consensus splice junction.

Prokaryotic features of a nucleus-encoded enzyme. cDNA sequences for chloroplast and cytosolic glyceraldehyde-3-phosphate dehydrogenases from mustard (Sinapis alba)

Two cDNA clones, encoding cytosolic and chloroplast glyceraldehyde-3-phosphate dehydrogenases (GAPDH) from mustard (Sinapis alba), have been identified and sequenced. Comparison of the deduced amino acid sequences with one another and with the GAPDH sequences from animals, yeast and bacteria demonstrates that nucleus-encoded subunit A of chloroplast GAPDH is distinct from its cytosolic counterpart and the other eukaryotic sequences and relatively similar to the GAPDHs of thermophilic bacteria. These results are compatible with the hypothesis that the nuclear gene for subunit A of chloroplast GAPDH is of prokaryotic origin. They are in puzzling contrast with a previous publication demonstrating that Escherichia coli GAPDH is relatively similar to the eukaryotic enzymes [Eur. J. Biochem. 150, 61-66 (1985)].

Nucleotide sequence of the Escherichia coli gap gene. Different evolutionary behavior of the NAD+-binding domain and of the catalytic domain of D-glyceraldehyde-3-phosphate dehydrogenase

A 1523-base-pair DNA fragment, spanning the gap gene from Escherichia coli, has been sequenced. It contains an open-reading frame whose length (330 amino acids) is in agreement with D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) molecular mass. This coding sequence is preceded by a Shine-Dalgarno complementary sequence and by two overlapping promoter-like structures. The codon usage within gap is consistent with that expected for a gene which is strongly expressed. The amino acid sequence of the E. coli GAPDH, deduced from the DNA sequence, contains all the amino acids postulated to play a functional role in GAPDH. Comparison of the E. coli enzyme with enzymes from other species reveals different evolutionary behaviour of the NAD+-binding domain and of the catalytic domain of GAPDH. The E. coli enzyme is found to be more similar to eucaryotic enzymes than to enzymes from thermophilic bacteria. This observation is discussed in terms of adaptation to growth at high temperature.

Various rat adult tissues express only one major mRNA species from the glyceraldehyde-3-phosphate-dehydrogenase multigenic family

We have isolated and sequenced a full-length cDNA clone encoding rat glyceraldehyde-3-phosphate-dehydrogenase (GAPDH, E.C.1.2.1.12). The entire mRNA is 1269 nucleotides long exclusive of poly(A) and contains respectively 71 and 196 bases of 5' and 3' non-coding regions. Primer extension as well as S1 nuclease protection experiments clearly established that a single (or at least a highly prominent) GAPDH mRNA species is expressed in all rat tissues examined. This sequence allowed the determination of the hitherto unknown primary structure of rat GAPDH which is 333 aminoacids long. Comparison between GAPDH sequences from rat, man and chicken revealed a high degree of sequence conservation at both nucleotide and protein levels.

The complete sequence of a full length cDNA for human liver glyceraldehyde-3-phosphate dehydrogenase: evidence for multiple mRNA species

A recombinant M13 clone (O42) containing a 65 b.p. cDNA fragment from human fetal liver mRNA coding for glyceraldehyde-3-phosphate dehydrogenase has been identified and it has been used to isolate from a full-length human adult liver cDNA library a recombinant clone, pG1, which has been subcloned in M13 phage and completely sequenced with the chain terminator method. Besides the coding region of 1008 b.p., the cDNA sequence includes 60 nucleotides at the 5'-end and 204 nucleotides at the 3'-end up to the polyA tail. Hybridization of pG1 to human liver total RNA shows only one band about the size of pG1 cDNA. A much stronger hybridization signal was observed using RNA derived from human hepatocarcinoma and kidney carcinoma cell lines. Sequence homology between clone 042 and the homologous region of clone pG1 is 86%. On the other hand, homology among the translated sequences and the known human muscle protein sequence ranges between 77 and 90%; these data demonstrate the existence of more than one gene coding for G3PD. Southern blot of human DNA, digested with several restriction enzymes, also indicate that several homologous sequences are present in the human genome.

Characterization of the transcription products of glyceraldehyde 3-phosphate-dehydrogenase gene in HeLa cells

We have partially purified the messenger RNA coding for glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) from HeLa cells and obtained a cDNA clone containing part of its sequence. Using this clone to probe electrophoregrams of RNA transferred to nitrocellulose, we have investigated the characteristics of nuclear and cytoplasmic transcripts in these cells. In the cytoplasm, nature GAPDH mRNA was detected in Northern blots as an intense band, apparently unique, of approximately 1400 nucleotides. The half-life of this mRNA was determined both from the decay kinetics, after a chase with actinomycin D, and from the labeling kinetics during an accumulation experiment. Both kinds of experiments yielded a half-life value of about 8 h, while the accumulation experiment indicated that steady-state GAPDH mRNA amounted to about 1.6% of cytoplasmic poly(A)-rich RNA. Much longer species, likely to be restricted to the nucleus, were also detected in RNA extracted from total cells. At least three discrete species of 1600, 4000, 5800 and 6800 bases were observed above a trailing background extending up to about 8000 bases. This value is commensurate with a functional size of the GAPDH transcription unit in the order of 13000 bases, which we determined by measuring the size of the ultraviolet inactivation target. Until direct evidence can be obtained at the genomic level, the present results provide the first clue to the existence of introns, presumably at least four, in a GAPDH gene from a higher eucaryote.

Post-transcriptional regulation of glyceraldehyde-3-phosphate-dehydrogenase gene expression in rat tissues

We have isolated and identified cDNA clones containing part of the coding sequence for rat glyceraldehyde-3-phosphate-dehydrogenase (GAPDH, E.C. 1.2.1.12). By using one of these clones as a probe, we have shown that: i) the abundance of GAPDH mRNA is different in various tissues of the adult rat and in good correlation with the abundance of the enzyme; ii) the transcription rates are quite similar in all tissues tested. We therefore conclude that the tissue-specific differential GAPDH gene expression is regulated by adjusting the abundance of its mRNA at the post-transcriptional level.