In many animal species, oocytes arrest in meiosis until they are fertilized. Over time, the quantity and quality of oocytes decreases, resulting in reduced fertility. Our goal is to better understand the regulation and function of ribonucleoprotein (RNP) granules that assemble in meiotically-arrested or stressed oocytes. The C. elegans adult germ line is an excellent model to study RNP granule dynamics due to the dramatic cellular changes that occur in response to meiotic arrest. To identify regulators of RNP granule assembly, we performed an RNAi screen that identified the Chaperone Containing Tcp-1 (CCT) family. We and others initially identified subsets of the eight cct genes as positive regulators of assembly of oocyte RNP granules and embryonic P granules (Updike and Strome, 2009; Hubstenberger et al., 2015; Wood et al., 2016). Our recent results, however, strongly suggest that all seven cct genes tested normally inhibit the accumulation of the MEX-3 RNA-binding protein into large aggregates in arrested oocytes. Thus, we have uncovered a novel role for CCT chaperone subunits in modulating RNP granules in the C. elegans germ line. In yeast and mammalian cells, select CCT subunits have also been identified as negative regulators of stress granules and of polyglutamine aggregation. To determine if CCT acts directly on MEX-3, or indirectly via effects on folding of microtubule subunits, we examined beta-tubulin. We find beta-tubulin levels are significantly reduced by knockdown of
cct-1 or
cct-2. Since prefoldin delivers microtubule and actin substrates to CCT, we also investigated the effects of knocking down prefoldin subunits. We find that while beta-tubulin levels are significantly reduced, MEX-3 granules are not affected, suggesting that the effects of CCT on RNP granules in arrested oocytes do not occur via the microtubule or actin cytoskeleton and may be direct. Our preliminary data suggest CCT also inhibits heat stress-induced MEX-3 granules. We are currently exploring the effect of CCTs on other RNP granule components, and ultimately hope that gaining a better understanding of the regulation of RNP granules will lead to insights into their function in the germ line.