In C. elegans, FOG-1 and FOG-3 directly promote spermatogenesis, and the activity of each gene is regulated by the TRA-1 transcription factor. as we reported earlier, the C.briggase
fog-3 promoter also has several TRA-1 binding sites and can work in C. elegans. To begin studying its native functuion, we made cbr-
fog-3(
v501), a frameshift mutation that creates a recessive null allele. It feminizes the germline in XX and XO animals but does not affect the soma. These phenotypes are just like those seen in C.elegans. Our phylogenetic analysis revealed that C. briggase
fog-3 promoter contains a second regulatory element, that is the unique 26 bp sequence is located near the first TRA-1 binding site, and is conserved in most Caenorhabditis species, but is not found in C.elegans. to study this site, we made the cbr-
fog-3(
v506) mutation, which scrambles the 26 bp conserved element. Surprisingly,
fog-3(
v506) causes dominant feminization of germ cells in both XX and XO animals. This phenotype is not suppressed by mutations in
tra-2 or
tra-1, and we can only maitian the strain by mating with wildtype males. To learn how this 26 bp element works, we used single worm RT-PCR to detect
fog-3 transcript levels in young XX animals. Our prelimary results suggested that
v506 mutants produce higher levels of
fog-3 transcripts than the wild type. this surprising result indicated that too much FOG-3 might disrupt function of the FOG-3/FOG-1 complex recently described by the Kimble lab. To test this model, we greated a cbr-
fog-3(
v501v506) double mutant. The addition of the
v501 frameshift mutation makes this double mutant recessive. we infer that
v506 normally causes a dominant Fog phenotype through the production of too much FOG-3 protein. Thus, all our data indicate the 26 bp element mediates repression of
fog-3, in addition to nearby TRA-1 binding sites. Furthermore, the loss of repression results in too much FOG-3, which might disrupt FOG-3/FOG-1 complex formation and function. The C. elegans
fog-3 promoter might compensate for the lack of this site by the presence of extra TRA-1 binding sites.