No abstract

The protamine mRNAs are stored for up to 8 days as translationally repressed ribonucleoprotein particles during murine spermatogenesis. Translational repression of the protamine 1, Prm1, mRNA is controlled by sequences in its 3'-untranslated region (UTR). In this study we used the yeast three-hybrid system to clone Msy4, which encodes a novel member of the Y box family of nucleic acid binding proteins. MSY4 specifically binds to a site within the 5' most 37 nucleotides in the Prm1 3' UTR. Msy4 is highly expressed in the testis, and the protein is detected in the cytoplasm of germ cells in both the testis and the ovary, where repressed messages are stored. Analysis of a previously described 48/50-kDa binding activity in testis extracts by electrophoretic mobility shift assays and immunoprecipitation indicates the activity is composed of MSY4 and MSY2, another mouse Y box protein. Polysome analysis demonstrates MSY4 is associated with mRNPs, consistent with MSY4 having a role in storing repressed messages.

The mouse Y-box proteins MSY2 and MSY4 are members of a protein family found in prokaryotes and eukaryotes that contain the highly conserved cold-shock domain (CSD). This 67-to 80-amino-acid (aa) nucleic acid binding domain is 43% identical from Escherichia coli to humans, contains the RNP1 and RNP2 RNA binding motifs, and forms a five-stranded antiparallel ␤-barrel structure (36). The prokaryotic members of this family, such as major cold-shock protein CspA in E. coli, are about 70 aa in length and are involved in the cold-shock response in various bacteria, an adaptive response to sudden temperature downshifts (14,19). CspA negatively regulates its own expression by acting as an RNA chaperone that destabilizes secondary structures in mRNA (1,17).The eukaryotic branch of the CSD family are Y-box proteins and have been characterized in all eukaryotes investigated, including fruit flies, planaria, goldfish, chickens, frogs, mice, and humans, with the exception of the yeast Saccharomyces cerevisiae (25,30). Y-box proteins are approximately 250 to 350 aa in length, have a CSD located in the amino-terminal half of the protein, and possess amino termini which are highly divergent in sequence and length (36). The carboxy tails of invertebrate Y-box proteins are quite variable in structure, with Drosophila melanogaster YPS containing RGG repeats, Caenorhabditis elegans LIN-28 containing zinc fingers, and Schistosoma mansoni SMYB1 containing a fibroin-like domain. On

Background: Ovarian folliculogenesis in mammals is a complex process involving interactions between germ and somatic cells. Carefully orchestrated expression of transcription factors, cell adhesion molecules and growth factors are required for success. We have identified a germ-cell specific, basic helix-loop-helix transcription factor, FIGLA (Factor In the GermLine, Alpha) and demonstrated its involvement in two independent developmental processes: formation of the primordial follicle and coordinate expression of zona pellucida genes.