The TRIM family protein, NHL-2, functions as a micro-RNA RISC co-factor in somatic tissues. NHL-2 is highly enriched in P-granules and the gonad core and
nhl-2 null mutants display multiple germline defects, including oocyte chromosomal defects, reduced brood size and embryonic lethality. We conducted a genome-wide RNAi screen to identify genes that lead to synthetic phenotypes when knocked down in
nhl-2 null mutants. Our screen identified the DEAD box RNA helicase,
drh-3, which is required for the biogenesis of CSR-1 and WAGO-1 22G small RNAs. Knockdown of
drh-3 in
nhl-2 null mutants leads to marked chromosomal abnormalities in diakinetic oocytes and anaphase embryos, as well as significantly enhanced embryonic lethality. Similar phenotypes were observed when
csr-1,
cde-1 or
ekl-1 were knocked down in
nhl-2 mutants. Furthermore, immunoprecipitation assays show that NHL-2 associates with CSR-1 and small RNA analysis of
nhl-2 null mutants display decreased levels of specific CSR-1 and WAGO-1 22G-RNAs, while levels of miRNAs and 21U-RNAs appear unchanged. These data suggest that
nhl-2 is required for normal levels of CSR-1 and WAGO-1 22G-RNAs and is required for the biogenesis or stability of these small RNAs. We hypothesize that the germline and chromosomal defects associated with
nhl-2 null mutants are likely due to deficiencies associated with CSR-1 22G-RNAs. Collectively, this study shows that NHL-2 is a novel co-factor of both CSR-1 and WAGO-1 22G-RNA pathways.