Dicer interacts with the P-granule component GLH-1: both localize to C. elegans nuclear pores and to stress-induced oocyte RNP granules

Abstract

P granules are ribonucleoprotein complexes specific to the cytoplasmic side of the nuclear pores of C. elegans germ cells. While P granules are implicated in post-transcriptional control of maternally-transcribed mRNAs, their function remains elusive. Our laboratory is particularly interested in the P-granule component GLH-1 (Germline RNA Helicase-1). Through genetic studies our laboratory has shown that GLH-1 is essential for fertility; however, the biochemical function of the GLH complex is still unknown. With immunoprecipitations and GST-pulldowns, we report that GLH-1 and the riboendonuclease Dicer bind one another and their interaction is not RNA dependent. Both GLH-1 protein and mRNA levels are reduced in the dcr- 1(ok247) mutant background; conversely, a reduction of DCR-1 protein in the glh-1(gk100) deletion strain is also observed. Thus, in complex in the C. elegans germline, these two proteins seem interdependent. In addition, evidence indicates Dicer protein levels, like those of GLH-1, are regulated by proteosomal degradation and are much increased when the Jun N-terminal kinase KGB-1 is missing in the kgb-1(um3) null. In the adult C. elegans germline DCR-1 is located throughout the cytoplasm as well as at the inner nuclear pores of the germ cell nuclei, in close opposition to GLH-1. Under stress conditions in oocytes GLH-1 and DCR-1 both re-locate and recruit other components to large cytoplasmic RNP granules. We hypothesize the GLH-1/DCR-1 complex may function in the transport, deposition, or regulation of maternally-transcribed mRNAs perhaps with their associated miRNAs.