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EMBO J. 2001 Mar 15;20(6):1363-72.

The TRA-1 transcription factor binds TRA-2 to regulate sexual fates in Caenorhabditis elegans.

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Department of Biochemistry, University of Wisconsin-Madison and Howard Hughes Medical Institute, 53706-1544, USA.


The tra-1 and tra-2 sex-determining genes promote female fates in Caenorhabditis elegans. Classical genetic studies placed tra-1 as the terminal regulator of the pathway with tra-2 acting upstream as a regulator of regulators of tra-1. Here we report the surprising result that the TRA-1 transcription factor binds the intracellular domain of the TRA-2 membrane protein. This binding is dependent on the MX regulatory domain, a region of the TRA-2 intracellular domain shown previously to be critical for the onset of hermaphrodite spermatogenesis. The functional importance of the TRA-1-TRA-2 physical interaction is supported by genetic interactions between tra-1(0) and tra-2(mx) mutations: a reduction of tra-1 gene dose from two copies to one copy enhances the tra-2(mx) feminization phenotype, but has no apparent somatic effect. In Caenorhabditis briggsae, we also find an MX-dependent interaction between Cb-TRA-1 and Cb-TRA-2, but intriguingly, no cross-species interactions are seen. The conservation of the TRA-1- TRA-2 interaction underscores its importance in sex determination.

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