[
International Worm Meeting,
2007]
The DEAD/DEAH-box family proteins are involved in various aspects of RNA metabolism such as transcription, pre-mRNA splicing, translation, RNA decay and ribosome biogenesis. These proteins are believed to have RNA helicase activity and also implicated in remodeling of RNA-protein complexes. C. elegans has over 50 DEAD/DEAH proteins, but the biological function of many of them remains unknown. We identified a DEAD-box protein F01F1.7 through our RNAi screen for genes essential for embryogenesis. It appears to be the ortholog of human DDX23 that was identified as a protein associated with U5 snRNP, and also shows significant homology to the yeast splicing factor PRP28. In the F01F1.7(RNAi) embryos, although approximately normal numbers of cells were produced, cell differentiation of various tissues was severely affected. Expression of differentiation markers for neurons, hypodermis, pharynx and intestine were not detected or significantly reduced in the terminally arrested F01F1.7(RNAi) embryos. In contrast, body muscle differentiation markers were always present, and P-granules normally distributed into two cells, supposedly Z2 and Z3 cells. This embryonic phenotype was distinct from that caused by general block of pre-mRNA splicing: RNAi of the core splicing component UAF-1 resulted in reduction of cell number (<200) and more robust block of cell differentiation, probably because of the lack of zygotic gene expression. Therefore, although its homologs in other organisms are implicated in pre-mRNA splicing, F01F1.7 appears not essential for splicing, at least in some tissues. When post-embryonic function of F01F1.7 was knocked-down by L1-soaking RNAi, the treated hermaphrodites reached adulthood without detectable morphological defects, but they produced only sperm (Mog phenotype). Interestingly, three known mog genes encode DEAH-box proteins whose yeast orthologs are components of the splicing machinery (MOG-1/PRP16, MOG-4/PRP2, and MOG-5/PRP22) (1, 2). RNAi of these genes also show embryonic lethality (2) whose phenotypes share some similarity to that of F01F1.7(RNAi). By analogy with the yeast splicing pathway, we speculate that F01F1.7 (PRP28 homolog) is a component of the MOG pathway, and that these DEAD/DEAH-box proteins regulate gene expression posttranscriptionally, probably through modulating ribonucleoprotein complexes.. 1. Puoti and Kimble (1999) MCB 19, 2189-2197. 2. Puoti and Kimble (2000) PNAS 97, 3276-3281.