Caenorhabditis elegans sex-determining GLI protein TRA-1A is regulated by sex-specific proteolysis.
Published: 2005
Language: eng
Number of pages: 239
Description: The C. elegans sex determination hierarchy specifies either one of two sexes: the hermaphrodite or the male. The  tra-1 gene is the global terminal regulator of the somatic sex determination pathway. Active TRA-1 promotes female fates in the hermaphrodite by repressing the transcription of genes that direct male development.The objective of the work presented here is to understand how the activity of TRA-1 is regulated. The tra-1 gene encodes two transcripts,  tra-1a and tra-1b. Males and hermaphrodites have similar levels of tra-1 transcripts, suggesting that  tra-1 is regulated post transcriptionally. Using a new antibody against TRA-1 in whole mount immunostaining I observed that TRA-1 appears to be much more abundant in hermaphrodites than in males. Western blot analysis revealed similar levels of TRA-1A and TRA-1B in lysates from males and hermaphrodites. Additional TRA-1-specific species (90-110 kDa) were present in the hermaphrodite lysates but absent from male lysates. These isoforms are the most abundant form of TRA-1 protein in hermaphrodites. The hermaphrodite-specific TRA-1 isoforms appear to be phosphoisoforms of a single TRA-1 band.Here I also describe the identification of proteins that specifically interact with FEM-2 in affinity chromoatography experiments. Loss-of-function mutants and RNAi silencing of three of these genes appear to partially phenocopy  fem-2 mutants.I show evidence that the hermaphrodite-specific isoform is generated by proteolytic processing of TRA-1A. Since the truncated TRA-1A isoforms are present in embryos before sexual differentiation is apparent, they are unlikely to be a result of female differentiation. Therefore I propose that these isoforms are responsible for the feminizing activity of the tra-1 gene. The truncation mapped to the region between amino acids 842 and 921. The observations that both a nonsense mutation that results in the production of a C-terminally truncated TRA-1A protein and truncated TRA-1A transgenes are feminizing, support my hypothesis that the truncated TRA-1 isoforms are responsible for the feminizing activity of the tra-1 gene.Genetic analyses indicate that the fem gene products regulate, directly or indirectly, the activity of TRA-1. Therefore, characterization of these putative FEM-2 binding proteins may identify the mechanism by which the FEMs regulate TRA-1 activity.
Notes: Source: Dissertation Abstracts International, Volume: 66-10, Section: B, page: 5217.

Thesis (Ph.D.)--University of Toronto, 2005.

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