Premature Translation of oskar in Oocytes Lacking the RNA-Binding Protein Bicaudal-C

ABSTRACT

Bicaudal-C (Bic-C) is required duringDrosophila melanogaster oogenesis for several processes, including anterior-posterior patterning. The gene encodes a protein with five copies of the KH domain, a motif found in a number of RNA-binding proteins. Using antibodies raised against the BIC-C protein, we show that multiple isoforms of the protein exist in ovaries and that the protein, like the RNA, accumulates in the developing oocyte early in oogenesis. BIC-C protein expressed in mammalian cells can bind RNA in vitro, and a point mutation in one of the KH domains that causes a strong Bic-C phenotype weakens this binding. In addition, oskar translation commences prior to posterior localization of oskar RNA in Bic-C ⁻ oocytes, indicating thatBic-C may regulate oskar translation during oogenesis.

ACKNOWLEDGMENTS

We thank Paul Macdonald for antibodies and members of the Lasko lab for useful discussions.

This work was supported by an operating grant to P.L. from the National Cancer Institute of Canada (NCIC), with funds from the Canadian Cancer Society, and by operating grants to S.R. from the Medical Research Council of Canada (MRC) and the Cancer Research Society. E.S. was supported in part by a Canada International Fellowship. P.L. is a research scientist of the NCIC. S.S. was supported in part by a graduate scholarship from the Fonds pour la formation de chercheurs et l’aide de recherche. K.R. was supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada. S.R. is an MRC Scholar.