BSF Binds Specifically to the bicoidmRNA 3′ Untranslated Region and Contributes to Stabilization ofbicoid mRNA

Abstract

The early stages of Drosophila melanogaster development rely extensively on posttranscriptional forms of gene regulation. Deployment of the anterior body patterning morphogen, the Bicoid protein, requires both localization and translational regulation of the maternal bicoid mRNA. Here we provide evidence that the bicoid mRNA is also selectively stabilized during oogenesis. We identify and isolate a protein, BSF, that binds specifically to IV/V RNA, a minimal form of the bicoid mRNA 3′ untranslated region that supports a normal program of mRNA localization during oogenesis. Mutations that disrupt the BSF binding site in IV/V RNA or substantially reduce the level of BSF protein lead to reduction in IV/V RNA levels, indicating a role for BSF in RNA stabilization. The BSF protein is novel and lacks all of the characterized RNA binding motifs. However, BSF does include multiple copies of the PPR motif, whose function is unknown but appears in other proteins with roles in RNA metabolism.

ACKNOWLEDGMENTS

This work was supported by grant GM42612 from the National Institutes of Health to P.M.M.

We thank members of the Macdonald lab for helpful discussions, Karen Kerr and Yemane Geddes for technical assistance, Amy Beaton of the BDGP for P element insertion stock l(2)k07109, the Bloomington Stock Center for fly stocks, and Tim Stearns for monoclonal anti-tubulin antibody. Mike Simon graciously provided lab space at a critical juncture.