1. Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706, USA
2. These authors contributed equally to this work.
3. Howard Hughes Medical Institute, Departments of Genetics and Medicine, University of WashingtonSeattle, USA 98195
4. Howard Hughes Medical Institute, Department of Medical Genetics and Laboratory of Cell and Molecular Biology, University of WisconsinMadison, Wisconsin 53706, USA

Correspondence to: Marvin P. Wickens¹ Correspondence and requests for materials should be addressed to M.W. (e-mail: Email: wickens@biochem.wisc.edu).

Abstract

The nematode Caenorhabditis elegans has two sexes, males and hermaphrodites. Hermaphrodites initially produce sperm but switch to producing oocytes. This switch appears to be controlled by the 3' untranslated region of fem-3 messenger RNA. We have now identified a binding factor (FBF) which is a cytoplasmic protein that binds specifically to the regulatory region of fem-3 3'UTR and mediates the sperm/oocyte switch. The RNA-binding domain of FBF consists of a stretch of eight tandem repeats and two short flanking regions. This structural element is conserved in several proteins including Drosophila Pumilio, a regulatory protein that controls pattern formation in the fly by binding to a 3'UTR. We propose that FBF and Pumilio are members of a widespread family of sequence-specific RNA-binding proteins.