Multiple mechanisms of polyadenylation site choice in male germ cells

Abstract

Polyadenylation, the process involved in the formation of the poly(A) tail at the 3¡¬ end of eukaryotic messenger RNAs (mRNAs), has been traditionally described as a two step process. However, the first and best understood step in the process ¡V polyadenylation site choice ¡V is an important source of regulation in polyadenylation. Polyadenylation site choice can be described as the association of the polyadenylation machinery with the mRNA around the site of polyadenylation, and changes in polyadenylation site choice can result in changes in the positioning of the polyadenylation site. The mechanism of polyadenylation site choice has been studied for over 30 years in somatic cells, and is therefore well-understood in that system. However, previous studies have indicated that male germ cells express many mRNAs that have different polyadenlyation sites than do somatic cells. These data suggest that male germ cells may have a different mechanism of polyadenylation site choice than somatic cells. In this dissertation, it is shown that male germ cell-specific polyadenylation sites are inefficiently used in somatic cells, that a male germ cell-expressed homolog of a known polyadenylation protein ¡V called ƒäCstF-64 ¡V is involved in polyadenylation site choice for at least some mRNAs in male germ cells, and that there may be another mechanism of polyadenylation site choice in male germ cells that is distinct from any previously-reported mechanism. Together, these data suggest that mammalian male germ cells have multiple mechanisms of polyadenylation site choice, and offer a possible explanation for why these cells show differences in polyadenylation site position.