Author Description

The transcription factor TRA-1 is the global regulator of sex determination in C. elegans. Hermaphrodite development requires TRA-1 activity, and in its absence males develop. Hermaphrodites accumulate high levels of a TRA-1 phosphoisoform (Mr ≈ 90-100kD) which we believe results from proteolytic cleavage of full-length TRA-1 (Mr = 135kDa). We hypothesized that PKA phosphorylation targets TRA-1 for proteolysis, thereby producing the active form of TRA-1.To test whether PKA is involved in sex determination, I expressed a constitutively active form of PKA (PKAc*) in adult animals. Increased PKA activity did not feminize the intestine of male worms, as judged by a lack of expression of hermaphrodite-specific fluorescent reporter constructs. Deletion of a cluster of potential PKA target sites from TRA-1 revealed that residues 650-679 are required for TRA-1 phosphorylation. Unexpectedly this phosphorylation is neither necessary for the production of the truncated isoform, nor is it required for any aspect of hermaphrodite development.