Submitted August 3, 2007
Returned for revision August 28, 2007
Accepted November 13, 2007
Gamete Biology
Pre-messenger RNA Cleavage Factor I (CFIm): Potential Role in Alternative Polyadenylation During Spermatogenesis
Becky L. Sartini ,
Hang Wang ,
Wei Wang ,
Clarke F. Millette ,
and
Daniel L. Kilpatrick *
* To whom correspondence should be addressed. E-mail: daniel.kilpatrick{at}umassmed.edu.
Abstract
A hallmark of male germ cell gene expression is the generation of cell-specific mRNAs by alternative polyadenylation, many of which utilize non-canonical A(A/U)UAAA-independent polyadenylation signals. Cleavage factor I (CFIm), a component of the pre-mRNA cleavage and polyadenylation protein complex, can direct A(A/U)UAAA-independent polyadenylation site selection of somatic cell mRNAs. Here we report that the CFIm subunits NUDT21/CPSF5 and CPSF6 are highly enriched in mouse male germ cells relative to somatic cells. Both subunits are expressed from spermatogenic cell mRNAs that are shorter than the corresponding somatic transcripts. Complementary DNA sequencing and Northern blotting revealed that the shorter Nudt21 and Cpsf6 mRNAs are generated by alternative polyadenylation in male germ cells using proximal poly(A) signals. Both sets of transcripts contain CFIm binding sites within their 3'-untranslated regions, suggesting auto-regulation of CFIm subunit formation in male germ cells. CFIm subunit mRNA and protein levels exhibit distinct developmental variation during spermatogenesis, indicating stage-dependent translational and/or post-translational regulation. CFIm binding sites were identified near the 3'-ends of numerous male germ cell transcripts utilizing A(A/U)UAAA-independent sites. Together these findings suggest that CFIm complexes participate in alternative polyadenylation directed by non-canonical poly(A) signals during spermatogenesis.
Key words:
Gamete Biology •
Testis •
Gene regulation •
Spermatogenesis
