Negative regulation of male development in Caenorhabditis elegans by a protein-protein interaction between TRA-2A and FEM-3

Abstract

The tra-2 gene of the nematode Caenorhabditis elegans encodes a predicted membrane protein, TRA-2A, that promotes XX hermaphrodite development. Genetic analysis suggests that tra-2 is a negative regulator of three genes that are required for male development: fem-1, fem-2, and fem-3. We report that the carboxy-terminal region of TRA-2A interacts specifically with FEM-3 in the yeast two-hybrid system and in vitro. Consistent with the idea that FEM-3 is a target of negative regulation, we find that excess FEM-3 can overcome the feminizing effect of tra-2 and cause widespread masculinization of XX somatic tissues. In turn, we show that the masculinizing effects of excess FEM-3 can be suppressed by overproduction of the carboxy-terminal domain of TRA-2A. A FEM-3 fragment that retains TRA-2A-binding activity can masculinize fem-3(+) animals, but not fem-3 mutants, suggesting that it is possible to release and to activate endogenous FEM-3 by titrating TRA-2A. We propose that TRA-2A prevents male development by interacting directly with FEM-3 and that a balance between the opposing activities of TRA-2A and FEM-3 determines sex-specific cell fates in somatic tissues. When the balance favors FEM-3, it acts through or with the other FEM proteins to promote male cell fates.

TRA-1 ChIP-seq reveals regulators of sexual differentiation and multilevel feedback in nematode sex determination

“…Somatic FEM-3 expression has not been shown previously (34) but is supported by genetic data: Somatic feminization of tra-1(gf) males is suppressed by gain-of-function mutations in the fem-3 3′ UTR that do not affect fem-3 transcript levels (26). Thus, FEM-3 activity is regulated through at least three separate means: The transmembrane receptor protein TRA-2 represses FEM-3 protein activity via physical interaction (35), fem-3 mRNA is negatively regulated via the 3′ UTR (36), and we find that fem-3 also is transcriptionally repressed by TRA-1. Therefore fem-3 appears to be an important node for control of the sex determination pathway.…”

mir-35 is involved in intestine cell G1/S transition and germ cell proliferation in C. elegans

“…Our experiments presented here show that mir-35-41 target multiple components of cell proliferation control pathways, to ensure correct cell numbers in the intestine and gonad. By qRT-PCR, we also found that mir-35-41 directly or indirectly regulate genes such as fem-2, fem-3 and xol-1, which all encode proteins required in the somatic sex determination pathway [62][63][64][65] (our unpublished data). It remains to be seen elusive if such a regulatory scheme of a miR-NA family applies to all multi-cell organisms.…”

The Caenorhabditis elegans F-box protein SEL-10 promotes female development and may target FEM-1 and FEM-3 for degradation by the proteasome

“…In XX animals, the her-1 gene, which encodes a secreted protein, is not expressed (2). The lack of her-1 expression in XX animals permits the activation of the transmembrane protein TRA-2, which blocks the functions of FEM-1 (a novel protein) (3), FEM-2 (a type 2C protein phosphatase) (4,5), and FEM-3 (an ankyrin-repeat protein) (6), possibly by interacting directly with FEM-3 (7). This block leads to the activation of the Zn-finger DNA-binding protein TRA-1 (8).…”