Dominant feminizing mutations implicate protein-protein interactions as the main mode of regulation of the nematode sex-determining gene tra-1.
The tra-1 gene is the terminal global selector of somatic sex in Caenorhabditis elegans: High tra-1 activity elicits female somatic development while low tra-1 activity elicits male development. Previous genetic studies defined a cascade of negatively interacting genes that regulates tra-1 activity in response to the primary sex-determining signal. Here, we investigate the last step in this regulatory cascade, by studying rare gain-of-function (gf) mutations of tra-1 that direct female somatic development irrespective of the upstream sex-determining signal. These mutations appear to abolish negative regulation of tra-1 in male tissues. We identify the lesions associated with 29 of these mutations and find that all affect a short stretch of amino acid residues present in both protein products of the tra-1 gene. Twenty-six alleles are associated with single nonconservative amino acid substitutions. Two alleles affect tra-1 RNA splicing and generate messages that omit part or all of the exon encoding this short stretch. These results suggest that sexual regulation of tra-1 is achieved post-translationally, by an inhibitory protein-protein interaction. The amino acid stretch altered by the tra-1(gf) mutations may define a site of interaction for negative regulators of tra-1. The stretch includes a potential phosphorylation site for glycogen synthase kinase 3 and may be conserved in the human gene GLI3, a homolog of tra-1 identified previously.
Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
M
M
de Bono
D
D
Zarkower
J
J
Hodgkin
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017238:Genes, Helminth / Q000235:genetics; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics; D018510:RNA, Helminth / Q000235:genetics; D012733:Sex Differentiation / Q000235:genetics*; D014157:Transcription Factors
D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D015801:Helminth Proteins; D008565:Membrane Proteins; D018510:RNA, Helminth; D014157:Transcription Factors; C121025:tra-1 protein, C elegans