Heat shock protein accumulation is upregulated in a long-lived mutant of Caenorhabditis elegans

We present evidence for elevated levels of heat shock protein 16 (HSP16) in an intrinsically thermotolerant, long-lived strain of Caenorhabditis elegans during and after heat stress. Mutation of the age-1 gene, encoding a phosphatidylinositol 3-kinase catalytic subunit, results in both extended life span (Age) and increased intrinsic thermotolerance (Itt) in adult hermaphrodites. We subjected age-synchronous cohorts of worms to lethal and nonlethal thermal stress and observed the accumulation of a small (16-18 kd) heat-shock-specific polypeptide detected by an antibody raised against C. elegans HSP16. Strains carrying the mutation hx546 consistently accumulated HSP16 to higher levels than a wild-type strain. Significantly, overaccumulation of HSP16 in the age-1(hx546) strain following heat was observed throughout the adult life span. A chimeric transgene containing the Escherichia coli beta-galactosidase gene fused to a C. elegans HSP16-41 transcriptional promoter was introduced into wild-type and age-1(hx546) backgrounds. Heat-inducible expression of the transgene was elevated in the age-1(hx546) strain compared with the wild-type strain under a wide variety of heat shock and recovery conditions. These observations are consistent with a model in which Age mutations exhibit thermotolerance and extended life span as a result of elevated levels of molecular chaperones.

The NED-8 conjugating system in Caenorhabditis elegans is required for embryogenesis and terminal differentiation of the hypodermis

This work has identified the enzymes involved in the activation and conjugation of the ubiquitin-like protein NED-8 in Caenorhabditis elegans. A C. elegans conjugating enzyme, UBC-12, is highly specific in its ability to utilize NED-8 as a substrate. Immunostaining shows that NED-8 is conjugated in vivo to a major target protein with a conjugate size of 90 kDa. While the amount of this conjugate is developmentally regulated with reduced levels in the larval stages, the mRNA encoding C. elegans UBC-12 is constitutively produced throughout development, as is NED-8 itself. The importance of the NED-8 conjugating system in C. elegans was determined by RNA interference (RNAi) assays using double-stranded RNA encoding NED-8, UBC-12, or the NED-8 activating enzyme component ULA-1. The progeny of both ned-8 and ubc-12 RNAi-treated hermaphrodites either arrested during embryonic development or underwent abnormal postembryonic development. The effect on postembryonic development was pleiotropic, the most frequent gross abnormality being vulval eversion during the L4 stage. Individuals with an everted vulva either burst at the L4 to adult molt or gave rise to adults incapable of egg laying. Additionally, both ned-8 and ubc-12 RNAi induced a striking abnormality in the alae, structures produced by the lateral hypodermal seam cells in the adult nematode. Affected alae were patchy and frequently diverged around a central space. Vulval defects were also produced by RNAi directed at C. elegans ula-1. This is the first demonstration of a requirement for NED-8 conjugation in metazoan development.

HSP43, a small heat-shock protein localized to specific cells of the vulva and spermatheca in the nematode Caenorhabditis elegans

Heat-shock protein 43 (HSP43) of Caenorhabditis elegans is prominently expressed in the utse cell, which attaches the uterus to the hypodermis, the uv1 cells joining the vulva and the uterus, the spermathecal valve and junctions between cells of the spermathecal cage. In body-wall muscle, HSP43 forms a punctate pattern of circumferential lines, probably corresponding to regions where the hypodermis contacts the muscle cells.

HSP25, a small heat shock protein associated with dense bodies and M-lines of body wall muscle in Caenorhabditis elegans

HSP25, a previously uncharacterized member of the alpha-crystallin family of small heat shock proteins in Caenorhabditis elegans, has been examined using biochemical and immunological techniques. HSP25 is the second largest of 16 identifiable small heat shock proteins in the nematode and is expressed at all developmental stages under normal growth conditions. Recombinant HSP25 produced in Escherichia coli exists predominantly as small oligomers (dimers to tetramers) and possesses chaperone activity against citrate synthase in vitro. In C. elegans, HSP25 is localized to dense bodies and M-lines in body wall muscle, to the lining of the pharynx, and to the junctions between cells of the spermathecal wall. Affinity chromatography of nematode extracts on a column of immobilized HSP25 resulted in specific binding of vinculin and alpha-actinin but not actin, as revealed by Western blotting. These results suggest a role for HSP25 in the organization or maintenance of the myofilament lattice and adherens junctions in C. elegans.

Feeding is inhibited by sublethal concentrations of toxicants and by heat stress in the nematode Caenorhabditis elegans: relationship to the cellular stress response

We report that the free-living nematode Caenorhabditis elegans can respond to a variety of stressors (compounds known to induce the production of cellular stress proteins in model biological systems), by ceasing pharyngeal pumping. This phenomenon results in both a reduction in intake of the stressor and a cessation of feeding. The effect of stressors can therefore be conveniently assayed by monitoring the decrease in the density of the bacterial food in liquid cultures of nematodes. A great range of stressors induced this response including alcohols, heavy metals, sulfhydryl-reactive compounds, salicylate, and heat. For several of these stressors, inhibition of pharyngeal pumping occurred at stressor concentrations below the threshold required for the induction of the 16-kDa heat shock proteins. Salicylate, which did not induce 16-kDa heat shock proteins at any concentration, nevertheless inhibited pharyngeal pumping. Heat was also inhibitory, at a temperature where 16-kDa heat shock protein production was near maximal. Some compounds caused only a partial inhibition of feeding while with others the effect was complete. Upon removal of the stressor, the nematodes resumed pharyngeal pumping with a residual inhibitory effect that depended on the concentration and type of stressor that had been applied. A number of C. elegans neurosensory mutant strains also exhibited a cessation of pharyngeal pumping when exposed to stressors suggesting that the mechanism underlying this inhibition was not entirely neurosensory and may be intrinsic to the pharynx. In C. elegans and other invertebrates, stress-induced inhibition of feeding may be an important survival mechanism that limits the intake of toxic solutes.

Caenorhabditis elegans small heat-shock proteins Hsp12.2 and Hsp12.3 form tetramers and have no chaperone-like activity

Four 12.2-12.6 kDa small heat-shock proteins (sHSPs) of Caenorhabditis elegans are the smallest known members of the sHSP family. They essentially comprise the characteristic C-terminal 'alpha-crystallin domain' of the sHSPs, having a very short N-terminal region, and lacking a C-terminal tail. Recombinant Hsp12.2 and 12.3 are characterized here. Far-UV CD spectra reveal, as for other sHSPs, predominantly a beta-sheet structure. By gel permeation and crosslinking, they are the first sHSPs shown to occur as tetramers, rather than forming the usual large multimeric complexes. Exceptionally, too, both appear devoid of in vitro chaperone-like abilities. This supports the notion that tetramers are the building blocks of sHSP complexes, and that higher multimer formation, mediated through the N-terminal domains, is a prerequisite for chaperone-like activity.

Subunit characterization of the Caenorhabditis elegans chaperonin containing TCP-1 and expression pattern of the gene encoding CCT-1

The chaperonin containing TCP-1 (CCT) from the free-living nematode Caenorhabditis elegans was purified and shown to contain at least seven subunit species ranging from 52-65 kDa. SDS-gel electrophoresis and Western blot analyses with antibodies against C. elegans CCT-1 and CCT-5 and an antibody which recognizes a conserved region in vertebrate CCT subunits confirm that the subunit compositions of CCTs from distantly related organisms (C. elegans and bovine species) are remarkably similar. Surprisingly, the co-purified HSP60 chaperonin present in the C. elegans CCT preparation has the greatest binding activity for denatured actin. Expression of a reporter gene under the control of the C. elegans cct-1 promoter is found to be mainly restricted to neuronal and muscle tissues, an observation which is consistent with the participation of CCT in actin and tubulin folding.

Structure-function studies on small heat shock protein oligomeric assembly and interaction with unfolded polypeptides

The small heat shock protein (smHSP) and alpha-crystallin genes encode a family of 12-43-kDa proteins which assemble into large multimeric structures, function as chaperones by preventing protein aggregation, and contain a conserved region termed the alpha-crystallin domain. Here we report on the structural and functional characterization of Caenorhabditis elegans HSP16-2, a 16-kDa smHSP produced only under stress conditions. A combination of sedimentation velocity, size exclusion chromatography, and cross-linking analyses on wild-type HSP16-2 and five derivatives demonstrate that the N-terminal domain but not most of the the C-terminal extension which follows the alpha-crystallin domain is essential for the oligomerization of the smHSP into high molecular weight complexes. The N terminus of HSP16-2 is found to be buried within complexes which can accommodate at least an additional 4-kDa of heterologous sequence per subunit. Studies on the interaction of HSP16-2 with fluorescently-labeled and radiolabeled actin and tubulin reveal that this smHSP possesses a high affinity for unfolded intermediates which form early on the aggregation pathway, but has no apparent substrate specificity. Furthermore, both wild-type and C-terminally-truncated HSP16-2 can function as molecular chaperones by suppressing the thermally-induced aggregation of citrate synthase. Taken together, our data on HSP16-2 and a unique 12.6-kDa smHSP we have recently characterized demonstrate that multimerization is a prerequisite for the interaction of smHSPs with unfolded protein as well as for chaperone activity.

Unique structural features of a novel class of small heat shock proteins

Small heat shock proteins (smHSPs) and alpha-crystallins constitute a family of related molecular chaperones that exhibit striking variability in size, ranging from 16 to 43 kDa. Structural studies on these proteins have been hampered by their tendency to form large, often dynamic and heterogeneous oligomeric complexes. Here we describe the structure and expression of HSP12.6, a member of a novel class of smHSPs from the nematode Caenorhabditis elegans. Like other members of its class, HSP12.6 possesses a conserved alpha-crystallin domain but has the shortest N- and C-terminal regions of any known smHSP. Expression of HSP12.6 is limited to the first larval stage of C. elegans and is not significantly up-regulated by a wide range of stressors. Unlike other smHSPs, HSP12.6 does not form large oligomeric complexes in vivo. HSP12.6 was produced in Escherichia coli as a soluble protein and purified. Cross-linking and sedimentation velocity analyses indicate that the recombinant HSP12.6 is monomeric, making it an ideal candidate for structure determination. Interestingly, HSP12.6 does not function as a molecular chaperone in vitro, since it is unable to prevent the thermally induced aggregation of a test substrate. The structural and functional implications of these findings are discussed.

An essential ubiquitin-conjugating enzyme with tissue and developmental specificity in th nematode Caenorhabditis elegans

The ubc-2 gene in Caenorhabditis elegans encodes a ubiquitin-conjugating enzyme (E2) homologous to yeast UBC4 and UBC5. UBC4 and UBC5 are individually dispensable class I E2 enzymes involved in the degradation of short-lived and abnormal proteins. Transgenic analysis using ubc-2-lacZ fusions and in situ immunofluorescence indicate that ubc-2 is abundantly expressed in most tissues of embryos and early larvae, but becomes specific to the nervous system in L4 larvae and adults. This suggests that the functions of this type of E2 are developmentally regulated in C.elegans. This hypothesis is supported by antisense analysis, which shows that blocking the expression of ubc-2 has a more severe effect in early developmental stages than in later stages. Through complementation of previously identified essential genes in the vicinity of ubc-2, we demonstrate that ubc-2 corresponds to let-70, a gene essential for C.elegans larval development. One let-70(ubc-2) allele contains a His75-->Tyr substitution, while another has an altered splice donor site.

Transgenic strains of the nematode C. elegans in biomonitoring and toxicology: effects of captan and related compounds on the stress response

The fungicide, captan, induces a cellular stress response in the soil nematode Caenorhabditis elegans. Transgenic C, elegans, which produce beta-galactosidase as a surrogate stress protein, reveal that captan-induced stress is localized mainly to muscle cells of the pharynx. The stress response is elicited by captan concentrations above 5 ppm and occurs within five hours of the initial exposure to the fungicide. Higher concentrations of captan, up to the solubility limit, increase the intensity of the response. Adult nematodes are significantly more sensitive to captan than are larvae. Captan also inhibits feeding in C. elegans, and nematodes exposed to captan rapidly cease muscular contractions in the pharynx. Stress induction and feeding inhibition are also caused by the related fungicides, captafol and folpet, but not by the parent compounds, phthalimide and tetrahydrophthalimide. The inhibition of feeding caused by compounds which elicit the cellular stress response may be an important survival mechanism for C, elegans.

Transgenic Caenorhabditis elegans strains as biosensors

Toxicity bioassays rely largely on lethality measurements. Such assays are generally lengthy and expensive, and provide little information on mechanisms of toxicity. A desire to understand the mechanisms by which cells respond to physical and chemical stresses has led to interest in measuring stress proteins as toxicological endpoints. Transgenic strains of the nematode Caenorhabditis elegans that carry a reporter enzyme under control of a stress-inducible promoter have been created. The reporter is easily quantified in intact nematodes, and it responds to a wide range of chemical stressors. Therefore, transgenic C. elegans can provide the basis for a wide range of quick, simple and informative bioassays.

Characterization of four new tcp-1-related cct genes from the nematode Caenorhabditis elegans

In this report we present the sequences of four new cct chaperonin genes from the nematode Caenorhabditis elegans. The four genes, cct-2, cct-4, cct-5, and cct-6 are orthologs of the mouse chaperonin genes Cctb, Cctd, Ccte, and Cctz, sharing 66%, 63%, 68%, and 67% deduced amino acid sequence identity, respectively. The C. elegans multigene family includes these four genes as well as cct-1 (tcp-1), and displays 23-35% pairwise predicted amino acid sequence identity between members, and 31-35% identity to the closely related archaebacterial chaperonin TF55. The five C. elegans cct genes are expressed in all life stages (egg, four larval stages, and adult). Members of the multigene family occur as a loosely associated group of three genes on chromosome II, and two widely separated genes on chromosome III. The predicted secondary structures of all five C. elegans CCT deduced protein sequences are nearly identical. Moreover, all chaperonins examined had comparable predicted secondary structures. Algorithmic predictions of the secondary structures of GroEL, Hsp60, and Rubisco subunit-binding protein (RuBP) are almost identical, and are very similar to the known GroEL secondary structure. The CCT/TF55 family predicted secondary structures are essentially identical to each other and are also related to GroEL, Hsp60, and RuBP. The most notable difference between the CCT/TF55 and the GroEL/Hsp60/RuBP families is in the presumed polypeptide binding domain.

Caenorhabditis elegans UBC-1, a ubiquitin-conjugating enzyme homologous to yeast RAD6/UBC2, contains a novel carboxy-terminal extension that is conserved in nematodes

The RAD6/UBC2 gene from Saccharomyces cerevisiae encodes a ubiquitin-conjugating enzyme involved in DNA repair, induced mutagenesis, and sporulation. Here we report the isolation and characterization of the Caenorhabditis elegans RAD6 homolog designated ubc-1. Ubc-1 encodes a 21.5-kD protein that shares considerable identity with RAD6 (66%) as well as with other RAD6 homologs, including Schizosaccharomyces pombe rhp6+ (70%), Drosophila melanogaster Dhr6 (83%), and the two human homologs HHR6A and HHR6B (84% and 83%, respectively). However, UBC-1 is distinct in being the only known RAD6 homolog, other than RAD6 itself, with a carboxy-terminal extension. Analysis of UBC-1 homologs from C. briggsae and Ascaris suum show that the presence of the carboxy-terminal extension is conserved in nematodes. When constitutively expressed from the yeast promoter ADH1, ubc-1 complements the DNA repair functions in a S. cerevisiae rad6 delta mutant. Surprisingly, ubc-1 fails to complement the sporulation function of RAD6, despite its possession of an acidic carboxy-terminal tail. C. elegans UBC-1 is capable of forming a thiol-ester bond with ubiquitin, but, unlike RAD6, is unable to transfer ubiquitin to histone H2B in vitro. Both cis and trans splicing are involved in the maturation of the ubc-1 transcript. The presence of the SL2 trans-splice leader in the ubc-1 transcript suggests that ubc-1 may be co-transcribed as part of a polycistronic message.

A portable regulatory element directs specific expression of the Caenorhabditis elegans ubiquitin gene ubq-2 in the somatic gonad

The Caenorhabditis elegans ubq-2 gene encodes a fusion of ubiquitin and a 52-amino-acid ribosomal protein. This single copy gene is both cis- and trans-spliced. It is expressed in all life stages of the worm and its transcript abundance is unaffected by heat stress. Transgenic analysis shows that expression of ubq-2 is regulated by an upstream promoter and a downstream element. The downstream element is required for ubq-2 promoter activity in embryos and in cells of the somatic gonad, including the distal tip cells, sheath cells, spermathecal cells, and cells of the uterus. The gonad-specific activity of the downstream regulator is transferable to a stress gene promoter such that heat-inducible expression of the transgene occurs in the somatic gonad. Stress-inducible beta-galactosidase expression in the gonad does not occur in all life stages, but is initiated late in the second or early in the third larval stage, when differentiation of gonadal tissues begins. Expression of a beta-galactosidase fusion protein from constructs containing the downstream ubq-2 regulator causes abnormalities of the gonad and embryonic lethality. Gonad abnormalities include arrested development and general disorganization. These abnormalities may be related to the overexpression of ubiquitin in the gonad.

Molecular analysis of Caenorhabditis elegans tcp-1, a gene encoding a chaperonin protein

A Caenorhabditis elegans (Ce) homologue to the eukaryotic tcp-1 gene (encoding t-complex polypeptide-1) has been mapped, isolated and sequenced. Ce tcp-1 is a single-copy gene located on chromosome II. Nucleotide sequence analysis of the gene reveals the presence of four introns in the coding region and repetitive elements upstream from the start codon. The predicted Ce TCP-1 protein displays more than 60% amino-acid sequence identity to other eukaryotic TCP-1, suggesting a common origin and function for these proteins. The primary tcp-1 transcript undergoes trans-splicing to the spliced leader SL1 RNA, in addition to cis-splicing, to yield a single mRNA species of 1.9 kb. Northern blot analysis shows that unlike the evolutionarily related Hsp60 chaperonin genes, tcp-1 is not upregulated at elevated temperatures, but instead appears to be down-regulated. Additionally, the overall level of the tcp-1 transcript is approximately constant throughout the development of the nematode. The Ce chaperonin-containing TCP-1 (CCT) was identified. A protein extract made from Ce embryos was subjected to sucrose gradient fractionation and ATP-agarose chromatography. Western blot analysis of the purified protein fractions, using anti-mouse TCP-1 monoclonal antibody and antibodies raised against Ce TCP-1, reveals that Ce TCP-1 is a 57-kDa protein subunit of a high-molecular-mass complex capable of binding ATP.

Novel ubiquitin-like ribosomal protein fusion genes from the nematodes Caenorhabditis elegans and Caenorhabditis briggsae

Among eukaryotes studied to date, homologs of the yeast 76-amino acid ribosomal protein have invariably been found to be cotranslated with ubiquitin. However, in the nematodes Caenorhabditis elegans and Caenorhabditis briggsae, a 70-amino acid domain with only 40% identity to ubiquitin is cotranslated with a homolog of the ribosomal protein. In the nematode ubiquitin-like (UbL) proteins, the nucleotide sequence of the UbL coding region is 92% identical in C. elegans and C. briggsae. The corresponding gene sequence contains a single intron at a location identical to that found in the polyubiquitin gene of C. elegans, further confirming that the ubl genes are evolutionarily related to ubiquitin. The ribosomal protein portion of the UbL polypeptide consists of 93 amino acids and is 68% identical to the human homolog. The ribosomal protein portion of UbL is longer than in other homologs, with the additional sequence being present as a basic carboxyl extension. The ubl gene is constitutively expressed in all life cycle stages of C. elegans. A comparison of the nematode UbL sequences with other ubiquitin-like genes reveals a pattern of sequence conservation, which suggests that the ubiquitin-like proteins may have conserved functional domains.

Targeted single-cell induction of gene products in Caenorhabditis elegans: a new tool for developmental studies

Heat shock promoters have been employed to achieve tightly regulated expression of transformed genes in a wide variety of model systems including tissue culture cells, bacteria, yeast, Drosophila, and more recently Caenorhabditis elegans. Here we investigate the feasibility of using a laser microbeam to induce a sub-lethal heat shock response in individual cells of C. elegans. We demonstrate that in transgenic strains carrying heat shock promoter-lacZ fusions, single cell expression of beta-galactosidase in a variety of cell types of endodermal, mesodermal, or ectodermal origin can be achieved after pulsing with a laser. A tissue-general, inducible promoter can therefore be converted into one of single cell specificity which can be induced rapidly at any point in development, offering unique opportunities to study cell-cell interactions in C. elegans. This technique defines a new approach to generate mosaic animals and may be adaptable to other organisms or tissues.

The ubc-2 gene of Caenorhabditis elegans encodes a ubiquitin-conjugating enzyme involved in selective protein degradation

The ubiquitin-protein conjugation system is involved in a variety of eukaryotic cell functions, including the degradation of abnormal and short-lived proteins, chromatin structure, cell cycle progression, and DNA repair. The ubiquitination of target proteins is catalyzed by a ubiquitin-activating enzyme (E1) and ubiquitin-conjugating enzymes (E2s) and in some cases also requires auxiliary substrate recognition proteins (E3s). Multiple E2s have been found, and these likely possess specificity for different classes of target proteins. Here we report the cloning and characterization of a gene (ubc-2) encoding a ubiquitin-conjugating enzyme which is involved in the selective degradation of abnormal and short-lived proteins in the nematode Caenorhabditis elegans. The nematode ubc-2 gene encodes a 16.7-kDa protein with striking amino acid sequence similarity to Saccharomyces cerevisiae UBC4 and UBC5 and Drosophila UbcD1. When driven by the UBC4 promoter, ubc-2 can functionally substitute for UBC4 in yeast cells; it rescues the slow-growth phenotype of ubc4 ubc5 mutants at normal temperature and restores their ability to grow at elevated temperatures. Western blots (immunoblots) of ubc4 ubc5 yeast cells transformed with ubc-2 reveal a protein of the expected size, which cross-reacts with anti-Drosophila UbcD1 antibody. C. elegans ubc-2 is constitutively expressed at all life cycle stages and, unlike yeast UBC4 and UBC5, is not induced by heat shock. Both trans and cis splicing are involved in the maturation of the ubc-2 transcript. These data suggest that yeast UBC4 and UBC5, Drosophila UbcD1, and C. elegans ubc-2 define a highly conserved gene family which plays fundamental roles in all eukaryotic cells.

Expression of the polyubiquitin-encoding gene (ubq-1) in transgenic Caenorhabditis elegans

The expression of the polyubiquitin-encoding gene (ubq-1) of Caenorhabditis elegans was analysed using transgenic nematode lines carrying translational ubq-1::lacZ fusions. Animals carrying a construct consisting of 938 bp of ubq-1 upstream sequences fused to lacZ (ubq938::lacZ) expressed beta Gal in embryos and in a tissue-general manner in 20% of L1 larvae. Somatic expression in later stages was usually confined to body muscle. Progressively larger deletions extending from the 5' end of ubq938::lacZ did not significantly alter the pattern of expression until 827 bp of sequence had been removed. Thus, sequences upstream from the transcription start point, including a G+C-rich block and a sequence resembling a TATA box (GAATAA), are not required to generate the expression pattern seen with ubq938::lacZ. Moreover, a basal level of expression was maintained in embryos when 903 bp were deleted. These results suggest that the promoter elements required for efficient expression of ubq-1 may reside within the transcribed region of the gene; alternatively, they must lie more than 1.7 kb upstream or 0.8 kb downstream from this region. Polymerase chain reaction analysis indicates that RNA molecules transcribed from the ubq938::lacZ and ubq delta 827::lacZ transgenes are trans-spliced to SL1, as is ubq-1 RNA.

Temporal and spatial expression patterns of the small heat shock (hsp16) genes in transgenic Caenorhabditis elegans

The expression of the hsp16 gene family in Caenorhabditis elegans has been examined by introducing hsp16-lacZ fusions into the nematode by transformation. Transcription of the hsp16-lacZ transgenes was totally heat-shock dependent and resulted in the rapid synthesis of detectable levels of beta-galactosidase. Although the two hsp16 gene pairs of C. elegans are highly similar within both their coding and noncoding sequences, quantitative and qualitative differences in the spatial pattern of expression between gene pairs were observed. The hsp16-48 promoter was shown to direct greater expression of beta-galactosidase in muscle and hypodermis, whereas the hsp16-41 promoter was more efficient in intestine and pharyngeal tissue. Transgenes that eliminated one promoter from a gene pair were expressed at reduced levels, particularly in postembryonic stages, suggesting that the heat shock elements in the intergenic region of an hsp16 gene pair may act cooperatively to achieve high levels of expression of both genes. Although the hsp16 gene pairs are never constitutively expressed, their heat inducibility is developmentally restricted; they are not heat inducible during gametogenesis or early embryogenesis. The hsp16 genes represent the first fully inducible system in C. elegans to be characterized in detail at the molecular level, and the promoters of these genes should find wide applicability in studies of tissue- and developmentally regulated genes in this experimental organism.

Isolation and characterization of eft-1, an elongation factor 2-like gene on chromosome III of Caenorhabditis elegans

A gene (eft-1) encoding an elongation factor 2-like protein was isolated from a region adjacent to the polyubiquitin gene, ubq-1, of Caenorhabditis elegans. Sequence analysis of genomic and cDNA clones revealed that the deduced amino acid sequence of the protein (EFT-1) is 38% identical to that of mammalian and Drosophila elongation factor 2 (EF-2). The entire eft-1 gene is approximately 3.8 kb in length and contains 5 exons separated by short introns of 46-75 bp. The 2,547-bp open reading frame predicts a protein of 849 amino acid residues (calculated Mr, 96,151). Conserved sequences shared among a variety of GTP-binding proteins including EF-2 are found in the amino-terminal third of EFT-1. The carboxy-terminal half contains regions with 40-57% similarity (including conservative changes) with segments characteristic of EF-2 and its prokaryotic homolog, EF-G. However, the histidyl residue target for ADP-ribosylation of EF-2 by diphtheria toxin is replaced by tyrosine in EFT-1. Southern and Northern blot analyses indicate that eft-1 is a single-copy gene that is expressed at all stages of nematode development. Amplification of fragments encoding highly conserved regions of EF-2 using the polymerase chain reaction led to the isolation of a fragment encoding the modifiable histidyl residue and which likely represents part of the C. elegans EF-2 gene (eft-2). This suggests that EFT-1 is not the C. elegans homolog of EF-2, but a closely related protein.

Molecular cloning and characterization of the Caenorhabditis elegans elongation factor 2 gene (eft-2)

A Caenorhabditis elegans lambda ZAP cDNA library was screened using a fragment amplified from highly conserved regions of the mammalian and Drosophila elongation factor 2 (EF-2). Two types of cDNA clones were obtained, corresponding to two mRNA species with 3'-untranslated regions of 60 and 115 nucleotides, both encoding identical polypeptides. Sequence analysis of these clones and comparisons with hamster and Drosophila EF-2 sequences suggests that they encode C. elegans EF-2. Clone pCef6A, encoding the entire C. elegans EF-2 mRNA sequence including 45 nucleotides of 5'-untranslated region, contains a 2,556-bp open reading frame which predicts a polypeptide of 852 amino acid residues (Mr 94,564). The deduced amino acid sequence is greater than 80% identical to that of mammalian and Drosophila EF-2. Conserved sequence segments shared among a variety of GTP-binding proteins are found in the amino-terminal region. The carboxy-terminal half contains segments unique to EF-2 and its prokaryotic homolog, EF-G, as well as the histidyl residue which is ADP-ribosylated by diphtheria toxin. The C. elegans protein contains a 12-amino-acid insertion between positions 90 and 100, and a 13-amino-acid deletion between positions 237 and 260, relative to hamster EF-2. Partial sequencing of a genomic clone encoding the entire C. elegans EF-2 gene (named eft-2) has so far revealed two introns of 48 and 44 bp following codons Gln-191 and Gln-250, respectively. Southern and Northern blot analyses indicate that eft-2 is a single-copy gene and encodes a 3-kb mRNA species which is present throughout nematode development.

Studies of the small heat shock proteins of Caenorhabditis elegans using anti-peptide antibodies

Peptides corresponding to selected regions of the 16 kDa small heat shock proteins (hsps) of the nematode C. elegans were synthesized and used to elicit polyclonal antibodies. It was found that these antibodies reacted predominantly with either the 16 kDa or the 18 kDa proteins, suggesting a close structural similarity between these hsps. Western blots of two-dimensional gels revealed extensive heterogeneity in these proteins, probably resulting from post-synthetic modifications. The native structures of both size classes of hsps were found to consist of large complexes of 4-5 x 10(5) Da.

The differentially expressed 16-kD heat shock genes of Caenorhabditis elegans exhibit differential changes in chromatin structure during heat shock

The 16-kD heat shock genes of Caenorhabditis elegans are encoded by four highly similar genes, arranged as divergently transcribed pairs. In spite of the high level of identity that exists between the HSP16 genes, after 2 hr of heat shock the mRNA from one locus accumulates at 7-14 times the level of that from the other locus. To determine if differential HSP16 gene transcriptional activity contributes to these differences, we examined the chromatin structure of the HSP16 genes in nonshocked embryos and in embryos undergoing both the initial phases of heat shock and after 2 hr of heat shock. To carry out these studies, we developed a nuclei isolation procedure that has allowed us to prepare large amounts of nuclei from C. elegans embryos, larvae, and adults that are essentially free of endogenous nuclease and protease activities and appear to be an excellent substrate for investigating chromatin structure in C. elegans. This procedure has enabled us to report the first observations of C. elegans basic chromatin structure, as well as characterize HSP16 chromatin structure in detail. The data suggest that differential HSP16 RNA accumulation following 2 hr of heat shock appears to be correlated with a change in the chromatin structure of one of the HSP16 loci to a preinduction, transcriptionally inactive configuration.

Differential regulation of closely related members of the hsp16 gene family in Caenorhabditis elegans

The heat-inducible genes encoding 16-kD heat shock polypeptides in Caenorhabditis elegans are found at two separate loci, one containing the 16-1 and 16-48 genes (locus A), and the other, the 16-2 and 16-41 genes (locus B). Despite the highly conserved structures of these genes and their promoters, the B locus produces up to sevenfold more mRNA during heat induction than does the A locus. Since there are two copies of the 16-1 and 16-48 genes at the A locus, the discrepancy in mRNA production is actually as high as 14:1 on a per gene basis. Measurements of the rate of hsp16 mRNA decay during recovery from a heat shock suggest that this difference is not caused by differential mRNA stability; furthermore, nuclear runon experiments yield rates of transcription for the 16-1/48 locus that are approximately threefold higher than those from the 16-2/41 locus. The higher levels of mRNA from the 16-2/41 locus, particularly at longer induction times, seem to be due to a marked difference in the temporal pattern of mRNA production from the two loci. While both loci are transiently activated by a heat shock, the 16-1 and 16-48 genes of the A locus are down-regulated to a lower transcription rate sooner than the genes from the B locus.

Reactivity of antinuclear antibodies with histones and other antigens in juvenile rheumatoid arthritis

Antinuclear antibodies are found in serum samples from most children with juvenile rheumatoid arthritis (JRA), but the antigenic specificities of these antibodies are not known. Using an immunoblot technique, we found that JRA patients' sera react with a variety of proteins in the nuclei of HEp-2 cells. Antibody to histone H1 was found in 42% of the JRA serum samples. An IgG antibody to a 45-kd protein was found in serum samples from some patients without uveitis, but it was not found in any sample from patients with uveitis. The immunoblot reactivity patterns do not appear to be useful in distinguishing between disease onset types or disease course types in patients with JRA.

Structure, organization, and expression of the 16-kDa heat shock gene family of Caenorhabditis elegans

Exposure of the nematode Caenorhabditis elegans to a heat shock results in the induction of a number of genes not normally expressed in the animals under normal growth conditions. Among these are a family of genes encoding 16 kDa heat shock proteins (hsp16s). The major hsp16 genes have been cloned and characterized, and found to reside at two clusters in the C. elegans genome. One cluster contains two distinct genes, hsp16-1 and hsp16-48, arranged in divergent orientations separated by only 348 base pairs (bp). An identical pair, duplicated and inverted with respect to the first pair, is located 415 bp away. This cluster, located on chromosome V, therefore contains four genes as two identical pairs within less than 4 kilobases of DNA, and the pairs form the arms of a large inverted repeat. A second pair of genes, hsp16-2 and hsp16-41, constitutes a second hsp16 locus with an organization very similar to that of the hsp16-1/48 locus, except that it is not duplicated. Comparisons of the derived amino acid sequences show that hsp16-1 and hsp16-2 form a closely related pair, as do hsp16-41 and hsp16-48. These hsps show extensive sequence identity with the small hsps of Drosophila, as well as with mammalian alpha-crystallins. The coding region of each gene is interrupted by a single intron of approximately 50 bp, in a position homologous to that of the first intron in mouse alpha-crystallin gene.(ABSTRACT TRUNCATED AT 250 WORDS)

UbiA, the major polyubiquitin locus in Caenorhabditis elegans, has unusual structural features and is constitutively expressed

Ubiquitin is a multifunctional 76-amino-acid protein which plays critical roles in many aspects of cellular metabolism. In Caenorhabditis elegans, the major source of ubiquitin RNA is the polyubiquitin locus, UbiA. UbiA is transcribed as a polycistronic mRNA which contains 11 tandem repeats of ubiquitin sequence and possesses a 2-amino-acid carboxy-terminal extension on the final repeat. The UbiA locus possesses several unusual features not seen in the ubiquitin genes of other organisms studied to date. Mature UbiA mRNA acquires a 22-nucleotide leader sequence via a trans-splicing reaction involving a 100-nucleotide splice leader RNA derived from a different chromosome. UbiA is also unique among known polyubiquitin genes in containing four cis-spliced introns within its coding sequence. Thus, UbiA is one of a small class of genes found in higher eucaryotes whose heterogeneous nuclear RNA undergoes both cis and trans splicing. The putative promoter region of UbiA contains a number of potential regulatory elements: (i) a cytosine-rich block, (ii) two sequences resembling the heat shock regulatory element, and (iii) a palindromic sequence with homology to the DNA-binding site of the mammalian steroid hormone receptor. The expression of the UbiA gene has been studied under various heat shock conditions and has been monitored during larval moulting and throughout the major stages of development. These studies indicate that the expression of the UbiA gene is not inducible by acute or chronic heat shock and does not appear to be under nutritional or developmental regulation in C. elegans.

Maturation of the major ubiquitin gene transcript in Caenorhabditis elegans involves the acquisition of a trans-spliced leader

Recently, studies on the 5'-ends of actin mRNAs in the nematode, Caenorhabditis elegans, have demonstrated that three of the four mature actin transcripts contain a 22-nucleotide leader sequence which is acquired by trans-splicing from a novel 100-nucleotide RNA. In the course of our studies of the ubiquitin genes in C. elegans (R. W. Graham and E. P. M. Candido, manuscript in preparation) we were led to the possibility that the major ubiquitin transcript in this organism might also contain a trans-spliced leader sequence. The 5'-noncoding region of the major ubiquitin gene (UbiA) contains a 3'-splice consensus sequence six nucleotides upstream of the initiation codon; however, sequencing of a further 1.6 kilobases upstream failed to reveal the existence of any potential 5'-splice sites in the correct relationship to known promoter elements. Furthermore, S1 and Northern blot analyses using probes complementary to upstream regions failed to detect the ubiquitin transcript. Primer extension experiments on total RNA using an oligonucleotide which hybridized to the ubiquitin transcript downstream of the 3'-splice site demonstrated the existence of a 22-nucleotide leader sequence not present in the ubiquitin gene 5'-region. Thus we show here that the 2500-nucleotide mRNA encoding a polyubiquitin precursor protein contains a 22-nucleotide leader sequence identical to that found in several C. elegans actin mRNAs and which is most likely acquired by a trans-splicing mechanism. In addition we have localized the site of transcript initiation for UbiA by S1 nuclease mapping.

Interaction of the mouse chromosomal protein HMG-I with the 3' ends of genes in vitro

High affinity mouse HMG-I binding sites have been distinguished from other (A+T)-rich sequences using band competition assays. These sites have been found 3' to the coding regions of a variety of genes. For the herpes simplex virus thymidine kinase and minute virus of mice genes, high affinity HMG-1 binding sites were further localized to the functional polyadenylation signal by DNase I footprinting. These results suggest that HMG-I may function at the 3' ends of genes in vivo.

Expression of intron-containing C. elegans heat shock genes in mouse cells demonstrates divergence of 3' splice site recognition sequences between nematodes and vertebrates, and an inhibitory effect of heat shock on the mammalian splicing apparatus

Splicing of a pair of intron-containing heat shock genes from Caenorhabditis elegans has been studied in transfected mouse cells. The hsp16-1 and hsp16-48 genes of C. elegans encode 16,000 Da heat shock polypeptides. Each gene contains a short intron of 52 (hsp16-1) or 55 (hsp16-48) base pairs. When these genes were introduced into mouse cells, they were efficiently induced following heat shock, but splicing of the introns was abnormal. In mouse cells, cleavage of the hsp16 transcripts occurred at the correct 5' splice sites, but the 3' splice sites were located at AG dinucleotides downstream of the correct sites. This aberrant splicing was not solely due to the small size of the C. elegans introns, since a hsp16-1 gene containing an intron enlarged by tandem duplication showed exactly the same splicing pattern. The mouse cells thus seem to be unable to recognize the natural 3' splice sites of the C. elegans transcripts. The efficiency of splicing was greatly reduced under heat shock conditions, and unspliced transcripts accumulated in the nucleus. During a subsequent recovery period at 37 degrees C, these transcripts were spliced and transported to the cytoplasm.

Structure, expression, and evolution of a heat shock gene locus in Caenorhabditis elegans that is flanked by repetitive elements

A locus containing two hsp16 genes in Caenorhabditis elegans has been characterized by DNA sequencing. Each gene encodes a 16-kDa polypeptide which is expressed following heat induction. The two genes, designated hsp16-2 and hsp16-41, are arranged in divergent orientations, and each contains a single intron of 46 and 58 base pairs, respectively. Although both gene transcripts are spliced efficiently in vivo, hsp16-41 corresponds to a previously isolated cDNA which contains an unspliced intron sequence. The 5'-noncoding regions of both genes contain TATA boxes preceded 18 or 19 nucleotides upstream by a heat shock regulatory sequence. The 3'-noncoding regions contain polyadenylation signals (AATAAA) either downstream (hsp16-2) or immediately adjacent (hsp16-41) to a sequence capable of forming a hairpin. This pair of hsp16 genes is flanked by three copies of an approximately 200-bp dispersed repetitive element (two copies on one side and a single one on the other side of the locus) which occurs in at least 70 copies throughout the C. elegans genome, and has been designated CeRep-16. Together with data described previously (Russnak, R. H., and Candido, E. P. M. (1985) Mol. Cell. Biol. 5, 1268-1278), the results presented here define a family of four distinct, related small heat shock protein genes. These are arranged in divergently transcribed pairs at two loci. The hsp16-48/41 genes code for one class of HSP16, 143-amino acid residues long, while the hsp16-1/2 genes encode the other class, which is 2 amino acid residues longer. Thus each locus codes for the two major types of HSP16. The two loci differ in a number of respects, including the presence of a tandem inverted duplication of two heat shock protein genes at one locus, and of repetitive elements at the other. Sequence comparisons allow us to propose a scheme for the evolution of the four genes and reveal conserved features of noncoding regions which may be involved in the regulation of their transcription, RNA processing, or translation. Using locus-specific hybridization probes, we have found that the genes at locus hsp16-2/41 are expressed at levels approximately 20-40-fold higher than those at locus hsp16-1/48.

Efficient transcription of a Caenorhabditis elegans heat shock gene pair in mouse fibroblasts is dependent on multiple promoter elements which can function bidirectionally

A divergently transcribed pair of Caenorhabditis elegans hsp16 genes was introduced into mouse fibroblasts by stable transfection with vectors containing bovine papillomavirus plasmid maintenance sequences and a selectable gene. The hsp16 genes were transcriptionally inactive in the mouse cells under normal growth conditions and were strongly induced by heat shock or arsenite. In a cell line with 12 copies of the gene pair, there were estimated to be more than 10,000 hsp16 transcripts in each cell after 2 h of heat shock treatment. The hsp16 transcript levels were more than 100 times higher than those of a gene with a herpes simplex virus thymidine kinase gene promoter carried on the same vector. A single heat shock promoter element (HSE) could activate bidirectional transcription of the two hsp16 genes when placed between the two TATA elements, but the transcriptional efficiency was reduced 10-fold relative to that of the wild-type gene pair. Four overlapping HSEs positioned between the two TATA elements resulted in inducible bidirectional transcription at greater than wild-type levels. The number of HSEs can therefore be a major determinant of the promoter strength of heat-inducible genes in mammalian cells. Partial disruption of an alternating purine-pyrimidine sequence between the two hsp16 genes had no significant effect on their transcriptional activity.

IS186: an Escherichia coli insertion element isolated from a cDNA library

Escherichia coli IS186 was isolated from cDNA libraries made from rainbow trout RNA and maintained in E. coli RR1. The element was 1,347 base pairs in length, had a perfect inverted repeat of 25 base pairs, and had an open reading frame of 375 amino acids. The hypothetical protein sequence of IS186 had limited homology to the E. coli IS4 hypothetical protein I sequence. There were three copies of IS186 in E. coli RR1.

Locus encoding a family of small heat shock genes in Caenorhabditis elegans: two genes duplicated to form a 3.8-kilobase inverted repeat

The genes coding for hsp 16-48, previously identified by cDNA cloning, and for another 16-kilodalton heat shock protein designated hsp16-1 were characterized by DNA sequencing. The two genes were arranged in a head-to-head orientation. Both the coding and flanking regions were located within a 1.9-kilobase module which was duplicated exactly to form a 3.8-kilobase inverted repeat structure. The inverted repeat structure ended in an unusual guanine-plus-cytosine-rich sequence 24 nucleotides in length. The identity of the two modules at the nucleotide sequence level implies that the duplication event may have occurred recently. Alternatively, gene conversion between the two modules could also maintain homology of the two gene pairs. The small heat shock genes of Caenorhabditis elegans contained TATA boxes and heat-inducible promoters, the latter agreeing closely with the Drosophila melanogaster consensus sequence described by Pelham (Cell 30:517-528, 1982). Unlike the homologous D. melanogaster genes, each of these C. elegans genes contained a short intron, the position of which has been conserved in a related murine alpha-crystallin gene. The intron separated variable and conserved regions within the amino acid sequences of the encoded heat shock polypeptides.

Inducibility of heat shock polypeptides in cells containing hyperacetylated histones

We have examined the effect of sodium butyrate on the levels of histone acetylation, the pattern of protein synthesis and the inducibility of heat shock polypeptides (hsps) in cultured trout fibroblasts. Maximal levels of histone acetylation are achieved upon treatment of these cells with 5 mM butyrate for 24 h. No significant changes in the pattern of protein synthesis, as detected by two-dimensional gel electrophoresis, are apparent under these conditions, although changes in the levels of three polypeptides are seen at shorter times of exposure to butyrate. Heat shock polypeptides are inducible at normal levels in butyrate-treated cells. This is in contrast to the ability of butyrate to inhibit the activation of steroid-inducible genes in some systems.

70-Kilodalton heat shock polypeptides from rainbow trout: characterization of cDNA sequences

RTG-2 cells, a line of fibroblasts from rainbow trout (Salmo gairdnerii), are induced to synthesize a distinct set of heat-shock polypeptides after exposure to elevated temperature or to low concentrations of sodium arsenite. We isolated and characterized two cDNA sequences, THS70.7 and THS70.14, encoding partial information for two distinct species of 70-kilodalton heat shock polypeptide (hsp70) from these cells. These sequences are identical at 73.3% of the nucleotide positions in their regions of overlap, and their degree of sequence conservation at the polypeptide level is 88.1%. The two derived trout hsp70 polypeptide sequences show extensive homology with derived amino acid sequences for hsp70 polypeptides from Drosophila melanogaster and Saccharomyces cerevisiae. Northern blot analysis of RNA from arsenite-induced RTG-2 cells, with the trout hsp70 cDNAs as probes, revealed the presence of three hsp70 mRNA species. Southern blot analysis of trout testis DNA cleaved with various restriction endonucleases revealed a small number of bands hybridizing to the hsp70 cDNAs, suggesting the existence of a small family of hsp70 genes in this species. Finally, trout hsp70 cDNA sequences cross-hybridized with restriction fragments in genomic DNA from HeLa cells, bovine liver, Caenorhabditis elegans, and D. melanogaster.

Histone deacetylase from HeLa cells: properties of the high molecular weight complex

In previous work [Hay, C. W., & Candido, E. P. M. (1983) J. Biol. Chem. 258, 3726-3734], we have shown that the histone deacetylase from HeLa cell nuclei is associated with a high molecular weight, nuclease-resistant complex. This complex was found to contain a variety of non-histone proteins, and indirect evidence for the importance of protein-protein interactions in the maintenance of its structure was obtained. In the present report, we examine the effects of beta-mercaptoethanol and neocuproine on the deacetylase complex and present data on the level of histone acetylation and the presence of satellite DNA sequences in this material. HeLa cell histone deacetylase complex partially dissociates in 10 mM beta-mercaptoethanol, resulting in a loss of non-histone proteins. The presence of 10 mM beta-mercaptoethanol during the micrococcal nuclease digestion of HeLa cell nuclei results in a greatly reduced yield of histone deacetylase complex, with a correspondingly large increase in the production of small oligonucleosomes and mononucleosomes. Histone deacetylase activity on endogenous labeled histone within the complex is strongly inhibited by either 1 or 10 mM beta-mercaptoethanol or 3 mM neocuproine. This loss of histone deacetylase activity does not seem to be due to an inactivation of the enzyme but appears to be a consequence of the disruption of the structure of the deacetylase complex itself. Histone H4 in the deacetylase complex prepared from HeLa cell nuclei by micrococcal nuclease digestion was more highly acetylated than H4 in bulk nucleosomes. Restriction enzyme analysis of the DNA associated with the histone deacetylase complex revealed neither an enrichment nor a depletion of major satellite sequences in this material.

Cloning and analysis of cDNA sequences coding for two 16 kilodalton heat shock proteins (hsps) in Caenorhabditis elegans: homology with the small hsps of Drosophila

The nucleotide sequences of two different cDNAs, CEHS48 and CEHS41, coding for the 16,000 dalton heat shock proteins (hsps) of Caenorhabditis elegans have been determined. CEHS48 codes for a polypeptide of 135 amino acids, approximately 15 fewer than the complete protein while CEHS41 is missing approximately 46 amino acids. From nucleotide 113 to the TAA termination signal the extent of homology between the sequences is 91%. Toward the 5' ends, the homology drops to 20% and results in completely divergent amino acid sequences. The 3' noncoding regions are only 30% homologous. Only CEHS48 contains a poly(A) signal and a poly(A) tail, suggesting that CEHS41 has an incomplete 3' end. The region from amino acid 43 to amino acid 115 shows extensive homology with corresponding regions in the four small hsps of Drosophila melanogaster and in mammalian alpha-crystallin. Two-dimensional gel analysis of in vitro synthesized hsp16 reveals the existence of five distinct components of identical molecular weights, but with different isoelectric points.

Histone deacetylase. Association with a nuclease resistant, high molecular weight fraction of HeLa cell chromatin

The chromatin-bound histone deacetylase of HeLa cells has been studied using endogenous [3H]acetyl-labeled polynucleosomes containing the enzyme, prepared in the presence of 40 mM butyrate. Histone deacetylase was assayed upon removal of the butyrate, and it was found that active enzyme is found only in association with a high molecular weight complex. This deacetylase-containing complex is relatively resistant to digestion with micrococcal nuclease. No activity is found on mononucleosomes or oligonucleosomes. Up to 90% of labeled acetyl groups are removed from histone deacetylase complexes incubated in the absence of butyrate. Free histones are a poor substrate under these conditions, but histones in mononucleosomes are deacetylated when they are incubated with histone deacetylase complex. Histone deacetylase remains bound to this complex in 1-2 M NaCl and does not dissociate from it during its reaction with acetylated core histones. Under typical nuclease digestion conditions, the histone deacetylase complex contains DNA with a size distribution of 5-11 kilobase pairs and a variety of nonhistone proteins. Comparison of the protein composition of histone deacetylase complexes with that of nuclear matrix preparations shows some similarities. Taken together, the results on the chromatographic behavior, the DNA fragment sizes, and the protein composition of the deacetylase complex suggest that protein-protein interactions may be important in maintaining its structure and also in the binding of the deacetylase itself to the complex.

Induction of a novel set of polypeptides by heat shock or sodium arsenite in cultured cells of rainbow trout, Salmo gairdnerii

The heat-shock response has been characterized in cultured fibroblasts of the rainbow trout, Salmo gairdnerii. The response has been elicited by two different stress situations; cells were either subjected to higher temperatures than normal (27 to 29 degrees C as opposed to 22 degrees C) or were incubated in medium containing sodium arsenite (15 to 100 microM final concentration). The response of the cells to these conditions is to synthesize a set of new polypeptides, the "heat-shock polypeptides" (hsps), that are not present or present in extremely low amounts in noninduced cells. Furthermore, during prolonged arsenite induction, the synthesis of normal cellular proteins is repressed. In trout fibroblasts, at least six hsps are detectable. These range from 30 000 to 87 000 in molecular weight and are referred to as hsp30, hsp32, hsp42, hsp62, hsp70, and hsp87. The hsp30 and hsp70 components are the most abundant and can be visualized by Coomassie blue staining of gels after prolonged induction. The heat-shock response is a reversible process in trout cells. Results of in vitro translation of mRNA from induced cells indicate that the control of hsp induction may be at the transcriptional level. Hsp70 from trout comigrates with the major hsp from Drosophila melanogaster on sodium dodecyl sulfate - polyacrylamide gels, suggesting that this protein may be highly conserved in evolution.

The large high mobility group proteins of rainbow trout are localized predominantly in the nucleus and nucleoli of a cultured trout cell line

On the basis of immunofluorescence and biochemical studies, it has been suggested that the concentration of nonhistone chromosomal protein high mobility group 1 may be higher in the cytoplasm than in the nucleus of mammalian cells (Bustin, M., and Neihart, N. K. (1979) Cell 16, 181-189). In view of the possible implications of this finding, we have examined the in situ location of trout proteins HMG-T1 and HMG-T2, which are analogous to the mammalian proteins HMG-1 and HMG-2. Antibodies prepared against purified HMG-T2 were shown to react only with HMG-T1 and HMG-T2, but not with any other chromosomal proteins from trout. This has been established using a modified immunoautoradiographic techique involving CNBr-activated paper transfers of proteins separated on regular sodium dodecyl sulfate-polyacrylamide gels. Using the indirect immunofluorescence technique to examine the subcellular location of HMG-T (T1 and T2) proteins in a cultured cell line of rainbow trout, we find that these proteins are located primarily in the nucleus of these cells. The fluorescence in the nucleolar regions is even more intense than in the nonnucleolar regions. The cytoplasmic regions show only a weak fluorescence which may be due to low levels of HMG-T proteins in the cytoplasm, since preincubation of anti-HMG-T2 with purified HMG-T2 abolishes the nuclear as well as cytoplasmic fluorescence.

Proteins of the Drosophila melanogaster male reproductive system: two-dimensional gel patterns of proteins synthesized in the XO, XY, and XYY testis and paragonial gland and evidence that the Y chromosome does not code for structural sperm proteins

Testes and paragonial glands of Drosophila melanogaster wild-type males were labeled in vitro using (35S)methionine, and the proteins synthesized were analyzed by 2-dimensional gel electrophoresis. Testes and paragonial glands were also labeled in vivo by feeding male larvae 35S-labeled yeast and then dissecting the adult males. Approximately 1200 proteins were resolved by autoradiography of the gels. The in vitro method was shown to be more sensitive and to allow faithful synthesis of all proteins produced in vivo. [3H]Proline was also used to label testes, and no significant differences from the 35Spattern were noted. Testes and paragonial glands from XO and XYY males were labeled in vitro with [35S]methionine, and the proteins synthesized were compared to those produced by wild-type males of identical autosomal background. No differences attributable to the Y chromosome could be detected in the testes or paragonial gland samples. Pure sperm were dissected manually from in vivo labeled males and the proteins analyzed. Ninety-two proteins were detected, which were all synthesized in comparable amounts by XO, XY, and XYY males, showing that the Y chromosome does not code for any of these structural sperm proteins. It is postulated that no Y chromosome products were detected because they are organizational or regulatory proteins present only in very small amounts in the adult testes. 35S-labeled males were also mated to unlabeled females and the transferred proteins analyzed on two-dimensional PAGE. The contributions of the testis and paragonial gland to the ejaculate were determined.

Partial inhibition of histone deacetylase in active chromatin by HMG 14 and HMG 17

Digestion of isolated Friend erythroleukemic cell nuclei with DNase I under conditions which selectively destroy the DNA of transcriptionally "active" genes releases into the supernatant fraction proteins of the non-histone "High Mobility Group" (HMGs). Two of these, HMG-14 and HMG-17(identified by solubility in trichloroacetic acid, electrophoretic mobility on SDS-polyacrylamide gels and by amino acid composition) will partially inhibit the endogenous mouse cell histone deacetylase enzymes when added to in vitro assay mixtures. Other closely related proteins do not share this inhibitory ability and thus the reaction with the enzymes appears to be specific. Since these two HMG proteins appear to be preferentially associated with the "active" fraction of chromatin, these findings have important implications for possible models of eukaryotic gene regulatory mechanisms.