X-chromosome-counting mechanisms that determine nematode sex.
Sex is determined in Caenorhabditis elegans by an X-chromosome-counting mechanism that reliably distinguishes the twofold difference in X-chromosome dose between males (1X) and hermaphrodites (2X). This small quantitative difference is translated into the 'on/off' response of the target gene, xol-1, a switch that specifies the male fate when active and the hermaphrodite fate when inactive. Specific regions of X contain counted signal elements whose combined dose sets the activity of xol-1. Here we ascribe the dose effects of one region to a discrete, protein-encoding gene, fox-1. We demonstrate that the dose-sensitive signal elements on chromosome X control xol-1 through two different molecular mechanisms. One involves the transcriptional repression of xol-1 in XX animals. The other uses the putative RNA-binding protein encoded by fox-1 to reduce the level of xol-1 protein. These two mechanisms of repression act together to ensure the fidelity of the X-chromosome counting process.
Nicoll
M
M
Department of Molecular and Cell Biology, University of California at Berkeley, 94720-3204, USA.
Akerib
C C
CC
Meyer
B J
BJ
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins; D002874:Chromosome Mapping; D012734:Disorders of Sex Development / Q000235:genetics; D018628:Gene Dosage; D005786:Gene Expression Regulation; D017238:Genes, Helminth; D017930:Genes, Reporter; D015801:Helminth Proteins / Q000235:genetics / Q000502:physiology; D007621:Karyotyping; D008297:Male; D009154:Mutation; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D012733:Sex Differentiation / Q000235:genetics*; D014158:Transcription, Genetic; D014960:X Chromosome
D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D016601:RNA-Binding Proteins; C091429:XOL-1 protein, C elegans