Polyadenylation is critical for mRNA stability and translational activation. During oocyte maturation and early embryonic development, cytoplasmic polyadenylation of preexisting mRNAs promotes their translation. The C. elegans
gld-2 gene is required for multiple steps in germline development, including the mitosis/meiosis decision. GLD-2 is a cytoplasmic poly(A) polymerase (PAP) that lacks an RNA recognition motif (1); similar PAPs have been identified in virtually all eukaryotic organisms (2). A yeast two-hybrid screen using GLD-2 as bait isolated GLD-3, RNP-8 and LARP-1 (1; L. Wang and J. Kimble, unpublished). GLD-2 has little PAP activity on its own, but it is stimulated in vitro by GLD-3 (1). We have now focused on RNP-8 to ask whether this GLD-2 interactor also stimulates GLD-2 activity and to determine whether RNP-8 has a major role in germline development. Preliminary data reveal that
rnp-8(RNAi) and
gld-2 mutants have similar defects during oogenesis. Both
gld-2 and
rnp-8 mRNAs are abundant in embryos, L4 larvae, and adults, and
rnp-8 mRNA is enriched in the germ line. To test whether RNP-8 stimulates the GLD-2 PAP activity, we performed assays for PAP activity in vitro. Preliminary data suggest that RNP-8 can indeed stimulate GLD-2 PAP activity. Taken together, we suggest that RNP-8 stimulates GLD-2 activity to control germline development.1. Wang, L., Eckmann, C.R., Kadyk, L.C., Wickens, M., and Kimble J. (2002), A regulatory cytoplasmic poly(A) polymerase in Caenorhabditis elegans. Nature 419: 312-316 2. Kwak, J.E., Wang, L., Ballantyne, S., Kimble J. and Wickens, M. (2004), Mammalian GLD-2 homologs are poly(A) polymerases. PNAS 101: 4407-4412