RNA helicase A (RHA) is a conserved protein with roles in transcription regulation and histone modification in numerous organisms such as flies and humans. We are studying the role of C. elegans RHA (RHA-1) in transcription regulation and germline development. A null mutant,
rha-1(
tm329), has a temperature-dependent defect in germline transcriptional silencing, and these defects lead to a sterile phenotype with few germ cells produced in hermaphrodite and male worms (Walstrom, Schmidt, Bean, and Kelly (2005) Mech. Dev. 122, 707). Others have shown that
rha-1 is required for RNA interference in the germline (Robert et al. (2005) Genes Dev. 19, 782-787). We found that
rha-1 interacts genetically with
rde-2 and
mut-7. The RDE-2 and MUT-7 proteins are required for RNAi and physically associate with each other (Tops et al. (2005) NAR 33, 347). The precise roles of these two proteins and RHA-1 in RNAi are not well understood. Interestingly,
rde-2;
rha-1 mutants exhibit mutual repression. At 25 degC,
rde-2 hermaphrodites are sterile due to nonfertile sperm and Emo oocytes, but the
rde-2;
rha-1 mutants have mostly fertile oocytes. The
mut-7;
rha-1 mutant hermaphrodites have an enhanced phenotype in that they are infertile due to defective sperm at a lower temperature than either single mutant. Using real-time RT-PCR, we are measuring levels of specific small RNAs in all these mutants. Our preliminary results indicate that
rha-1 mutants have an increased level (2-4X) of some small RNAs while
rde-2 and
mut-7 mutants have decreased levels of the same small RNAs. The mutual suppression of the
rde-2;
rha-1 mutants could be explained by their near wild-type levels of small RNAs. We plan to expand these experiments to measure small RNA levels in both hermaphrodites and males.