Early embryonic developmental processes are regulated through the translation of maternal mRNAs prior to the onset of zygotic transcription. In many organisms, including Drosophila, Xenopus and the mouse, mRNA translation is regulated through the control of maternal mRNA poly[A] tail length. This process, termed cytoplasmic polyadenylation, is directed through a cis-acting uracil rich mRNA sequence termed the cytoplasmic polyadenylation element (CPE) and a cytoplasmic polyadenylation element binding protein (CPEB). Despite the recent advances in our knowledge concerning the importance of cytoplasmic polyadenylation in regulating early developmental processes in model organisms, it is not known if this process controls mRNA translation during human oocyte maturation. Recent studies in my laboratory have identified a human cDNA which shares extensive homology to both Xenopus and mouse CPEB sequences. We have evidence that the human CPEB mRNA is alternatively spliced and encodes CPEB proteins with different N-terminal extensions. Alternative splicing of CPEB mRNAs has not been previously reported. The mRNA encoding human CPEB is expressed at high levels in ovarian tissue, consistent with a possible role in regulating oocyte maturation. The studies proposed in this application are designed to test the hypothesis that the putative human CPEB encodes a bona fide CPE-binding protein which mediates cytoplasmic polyadenylation. We will characterize the functional role of the alternately spliced variants of the human CPEB mRNA which we have identified. This study will also identify human maternal mRNAs which encode candidate CPE sequences in their 3' untranslated regions. We will determine if translation of these mRNAs is subject to cytoplasmic polyadenylation-mediated control in a heterologous Xenopus assay system and during human oocyte maturation. Successful resolution of this study would establish a role for CPEB in human development and further our understanding of translational control through CPEB-mediated cytoplasmic polyadenylation in both human and model systems.

R03HD038081

2000-08-01

2002-06-30