REPRESSION BY THE 3'-UTR OF FEM-3 A SEX-DETERMINING GENE, RELIES ON AUBIQUITOUS MOG-DEPENDENT CONTROL IN CAENORHABDITIS-ELEGANS

The fem-3 sex-determining gene is repressed post-transcriptionally via a regulatory element in its 3' untranslated region (UTR) to achieve t he switch from spermatogenesis to oogenesis in the Caenorhabditis eleg ans hermaphrodite germ line. In this paper, we investigate the fem-3 3 ' UTR control in somatic tissues using transgenic reporter assays, and we also identify six genes essential for this control. First, we find that a reporter transgene bearing a wild-type fem-3 3' UTR is repress ed in somatic tissues, whereas one bearing a mutant fem-3 3' UTR is de repressed, Moreover, control by mutant 3' UTRs is temperature sensitiv e as predicted from the temperature sensitivity of the fem-3 gain-of-f unction (gf) mutations. Secondly, we find a fem-3 3' UTR RNA-binding a ctivity in somatic tissues, in addition to the previously reported ger mline-specific binding by FBF. Thirdly, we find that each of six genes , mog-1-mog-6, is required for repression by the fem-3 3' UTR, Therefo re, the mog genes not only affect the sperm/oocyte switch in the germ line, but also function in somatic tissues. We suggest that the mog ge nes may encode components of a ubiquitous machinery that is used for f em-3 3' UTR-mediated repression and the sperm/oocyte switch.