Molecular cloning and characterization of mouse testis poly(A) binding protein II encoded by the Pabp3 gene, which transcomplements meiotic mutant sme2 of S. pombe

A cDNA clone from a mouse testis cDNA library was isolated by the transcomp lementation method using a Schizosaccharomyces pombe meiotic mutant (sme2) that is defective in meiosis I. The cDNA clone isolated has an open reading frame encoding 302 amino acids constituting a protein with a strong simila rity to mouse poly(A) binding protein II (mPABII) and bovine poly(A) bindin g protein II (PABII). PABII is known to bind to the growing poly(A) tail an d stimulates poly(A) polymerase, which catalyzes the polymerization of the mRNA poly(A) tail. Northern blot analysis of the cDNA clone identified as m PABII revealed a single transcript of 1.2 kb. This was detectable exclusive ly in adult testis. Immunohistochemical analysis using a polyclonal antibod y demonstrated that mPABII protein was expressed in the nucleus at specific stages from late pachytene spermatocytes to round spermatids. Genetic mapp ing showed the Pabp3 gene encoding mPABII to be located near position 19.5 on mouse chromosome 14. These results suggest that mPABII might be involved in specific spermatogenetic cell differentiation.