Structure and expression of murine poly(A) binding protein Ⅱ gene

Abstract

Genomic DNA clone and cDNA clones encoding murine poly(A) binding protein II (mPAB II), a component of the mammalian 3``-end processing machinery, were isolated in this study. The overall structure of mPAB II consists of an acidic N-terminal domain, an RNA-binding domain in the middle, and a basic C-terminal domain. Sequence comparison of the cDNA clone with the genomic DNA clone reveals that the mPAB II gene has seven exons. Genomic structure of the mPAB II gene including the exon-intron arrangement shows significant homology with that of bovine PAB II. Southern blot analysis shows that the mPAB II gene has pseudogenes or related genes in mouse genome. Two mPAB II transcripts,3.6 kb and 2.1 kb,are present in all tissues. An additional 1.4 kb transcript which is generated by differential polyadenylation is most abundantly produced in a testis-specific manner. Primer extension analysis demonstrates the existence of multiple transcription start sites. At least four transcription factor binding sites are present in the promoter region. Two of them flank the multiple transcription start sites. The factors binding these sites are present in testis nuclear extract but not in liver nuclear extract. The results suggest that transcription of the mPAB II gene in testis may be activated by these presumptive testis-specific factors. The expression level of mPAB II is higher in testis, especially in round spermatids, than in brain. These results suggest that the excessive expression of the mPAB II gene in testis, particularly in round spermatids, is related to the synthesis and the accumulation of all the mRNAs necessary for spermiogenesis.