Control of the sperm-oocyte switch in Caenorhabditis elegans hermaphrodites by the fem-3 3' untranslated region.
In the Caenorhabditis elegans hermaphrodite germ line, sperm and then oocytes are made from a common pool of germ-cell precursors. The decision to differentiate as a sperm or an oocyte is regulated by the sex-determining gene, fem-3. Expression of fem-3 in the hermaphrodite germ line directs spermatogenesis and must be negatively regulated to allow the switch to oogenesis. In adult hermaphrodites (which are producing oocytes), most fem-3 RNA is found in the germ line, consistent with both the requirement for fem-3 in hermaphrodite spermatogenesis and the maternal effects of fem-3 on embryonic sex determination. Whereas loss-of-function mutants in fem-3 produce only oocytes, hermaphrodites carrying any of nine fem-3 gain-of-function (gf) mutations make none; instead sperm are produced continuously and in vast excess over wild-type amounts. Genetic analyses suggest that fem-3(gf) mutations have escaped a negative control required for the switch to oogenesis. Here we report that all nine fem-3(gf) mutants carry sequence alterations in the fem-3 3' untranslated region (3' UTR). There is no increase in the steady-state level of fem-3(gf) RNA over wild-type, but there is an increase in the polyadenylation of fem-3(gf) RNA that is coincident with the unregulated fem-3 activity. Results of a titration experiment support the hypothesis that a regulatory factor may bind the fem-3 3' UTR. We speculate that fem-3 RNA is regulated through its 3' UTR by binding a factor that inhibits translation, and discuss the idea that this control may be part of a more general regulation of maternal RNAs.
Department of Biochemistry, College of Agricultural and Life Sciences, Graduate School, University of Wisconsin-Madison 53706.
J
J
Ahringer
J
J
Kimble
D000818:Animals; D001483:Base Sequence; D002107:Caenorhabditis / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics; D012734:Disorders of Sex Development; D005786:Gene Expression Regulation; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000166:cytology*; D009866:Oogenesis / Q000235:genetics; D010957:Plasmids; D014176:Protein Biosynthesis; D012313:RNA / Q000235:genetics; D012732:Sex Determination Analysis; D013091:Spermatogenesis / Q000235:genetics; D013094:Spermatozoa / Q000166:cytology*; D014170:Transformation, Genetic
D012313:RNA