The Promoter of the Poly(A) Binding Protein 2 (Pabp2) Retroposon Is Derived from the 5′-Untranslated Region of the Pabp1 Progenitor Gene

Abstract

The mouse Pabp2 retroposon encodes an isoform of poly(A) binding protein that is expressed in meiotic and early haploid spermatogenic cells. In the present study, we have determined the transcription start site of the Pabp2 gene to clarify the source of its promoter, a prerequisite for expression of retroposons and preservation of their function by natural selection. The 5′ end of the mouse Pabp2 retroposon exhibits extensive similarity to the entire 5′ UTR of the human PABP1 mRNA, but there is no similarity upstream of the transcription start site of the human PABP1 mRNA, indicating that the Pabp2 gene lacks 5′ flanking sequences of the parental PABP1 gene. Oligonucleotide-directed RNase H cleavage and 5′ rapid amplification of cDNA ends both indicate that the transcription start site of the mouse Pabp2 gene is located ∼330 bases downstream of the capsite of the PABP1 mRNA, indicating that the Pabp2 promoter is derived from the PABP1 5′ UTR.