VBH-1 is a DEAD-box RNA helicase closely related to Vasa and Belle from D. melanogaster. DEAD-box RNA helicases resolve misfolded RNA regulating in this way RNA-RNA and RNA-protein interactions. VBH-1 is important for embryogenesis and gametogenesis, and plays an important role in the sperm/oocyte switch in the hermaphrodite gonad. VBH-1 associates constitutively to P granules, but is also found in the cytoplasm of all blastomeres during embryogenesis, and in the male and hermaphrodite gonad. In this work we found that following different kinds of stress (heat-shock, starvation, sperm depletion) VBH-1 associates to granules in the gonad core, oocytes, and in both somatic and germline blastomeres during early embryogenesis. In every case, VBH-1 granules localized with or near CGH-1-positive granules. CGH-1 is a DEAD-box helicase usually found in small cytoplasmic foci that might resemble processing bodies, which under stress conditions aggregates into bigger foci. Intriguingly VBH-1 association to these granules does not depend on a single sequence since three different non-overlapping fragments that comprise the entire sequence are able to localize into foci after heat shock. To further understand the possible role of VBH-1, and its closest homolog in worms (LAF-1) in stress response, we made a lifespan assay at 37 deg C and found that vbh-1(RNAi) and laf-1(RNAi) animals were more sensitive to heat-shock than control animals. We found that VBH-1 is also expressed at low levels in the soma by Western Blot analysis using extracts from the germline proliferation defective mutant glp-4(bn2). Seemingly, this somatic expression is responsible for VBH-1 mediated response to stress since germline-specific silencing of vbh-1 had no effect on animals survival at 37 deg C. Our work points towards a previously unknown role of VBH-1 during different kinds of stress. We are currently working on finding of mRNA targets of VBH-1 during stress; so far we have found the down-regulation of a small heat-shock protein in vbh-1(RNAi) animals.

Affiliation:
- Departamento de Biol Celular y del Desarrollo, Instituto de Fisiologia Celular, Universidad Nacional Autonoma de Mexico, Mexico,D.F., Mexico