The goa-1 gene encoding the alpha subunit of the heterotrimeric guanosine triphosphate-binding protein (G protein) Go from Caenorhabditis elegans is expressed in most neurons, and in the muscles involved in egg laying and male mating. Reduction-of-function mutations in goa-1 caused a variety of behavioral defects including hyperactive movement, premature egg laying, and male impotence. Expression of the activated Go alpha subunit (G alpha o) in transgenic nematodes resulted in lethargic movement, delayed egg laying, and reduced mating efficiency. Induced expression of activated G alpha o in adults was sufficient to cause these phenotypes, indicating that G alpha o mediates behavior through its role in neuronal function and the functioning of specialized muscles.

To elucidate the cellular role of the heterotrimeric G protein G o , we have taken a molecular genetic approach in Caenorhabditis elegans. We screened for suppressors of activated GOA-1 (G o ␣) that do not simply decrease its expression and found mutations in only two genes, sag-1 and eat-16. Animals defective in either gene display a hyperactive phenotype similar to that of goa-1 loss-of-function mutants. Double-mutant analysis indicates that both sag-1 and eat-16 act downstream of, or parallel to, G o ␣ and negatively regulate EGL-30 (G q ␣) signaling. eat-16 encodes a regulator of G protein signaling (RGS) most similar to the mammalian RGS7 and RGS9 proteins and can inhibit endogenous mammalian G q /G 11 in COS-7 cells. Animals defective in both sag-1 and eat-16 are inviable, but reducing function in egl-30 restores viability, indicating that the lethality of the eat-16; sag-1 double mutant is due to excessive G q ␣ activity. Analysis of these mutations indicates that the G o and G q pathways function antagonistically in C. elegans, and that G o ␣ negatively regulates the G q pathway, possibly via EAT-16 or SAG-1. We propose that a major cellular role of G o is to antagonize signaling by G q .

In a screen for suppressors of activated GOA-1 (G␣ o ) under the control of the hsp-16.2 heat-shock promoter, we identified three genetic loci that affected heat-shock-induced GOA-1 expression. The cyl-1 mutants are essentially wild type in appearance, while hsf-1 and sup-45 mutants have egg-laying defects. The hsf-1 mutation also causes a temperature-sensitive developmental arrest, and hsf-1 mutants have decreased life span. Western analysis indicated that mutations in all three loci suppressed the activated GOA-1 transgene by decreasing its expression. Heat-shock-induced expression of hsp-16.2 mRNA was reduced in cyl-1 mutants and virtually eliminated in hsf-1 and sup-45 mutants, as compared to wild-type expression. The mutations could also suppress other transgenes under heat-shock control. cyl-1 and sup-45, but not hsf-1, mutations suppressed a defect caused by a transgene not under heat-shock control, suggesting a role in general transcription or a post-transcriptional aspect of gene expression. hsf-1 encodes the C. elegans homolog of the human heat-shock factor HSF1, and cyl-1 encodes a cyclin most similar to cyclin L. We believe HSF-1 acts in heat-shock-inducible transcription and CYL-1 acts more generally in gene expression. Hajdu-Cronin et al. 1999;. One of the most-studied examples of inducible tranLackner et al. 1999), as well as mutations affecting gene expression, which we describe here. scription in eukaryotes is heat-shock induced mRNA synthesis, a stress survival mechanism that results in ele-RNA polymerase II (Pol II) catalyzes transcription of all protein-coding genes in eukaryotes (reviewed by vated expression of heat-shock genes and diminished expression of other genes. In most eukaryotes, heatProudfoot et al. 2002). After recruitment to a promoter ("initiation"), Pol II transcribes a short RNA of ‫04-02ف‬shock-induced transcription requires activation of the heat-shock factor (HSF) and binding of HSF to specific nucleotides and then pauses. Phosphorylation of the carboxyl terminal domain (CTD) of Pol II enables capsequence motifs on the promoter called heat-shock elements (HSE; Lis and Wu 1993). HSF is synthesized and ping of the emerging RNA and resumption of transcription by Pol II ("elongation"). Phosphorylation also resequestered at a constant level in the cells under normal conditions . Saccharomyces cerevisiae and Drocruits mRNA processing factors to the CTD. During elongation, introns are removed by pre-mRNA splicing, sophila melanogaster each have one HSF, which functions similarly to HSF1 in higher animals (Morimoto 1998). the mRNA is packaged for export to the cytoplasm, and the CTD is dephosphorylated. While initiation, elongaUnder unstressed conditions, HSF exists as an inactive monomer in most eukaryotes. Stress causes HSF to trition, and processing were thought to occur sequentially merize and bind to the HSE with high affinity (Westwood et al. 1991), resulting in transcription of heatshock proteins (hsp). In D. melanogaster, stress causes a Sequence data from this art...

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