DNA polymerase-beta and poly(ADP)ribose polymerase mRNAs are differentially expressed during the development of male germinal cells.

Abstract

We have examined the steady-state mRNA levels in spermatogenic cells of two nuclear enzymes that appear to be involved in DNA repair, DNA polymerase-beta (pol-beta) and poly(ADP)ribose polymerase (PADPRP). Two pol-beta mRNAs of 1.3 kb and 1.4 kb were detected in extracts from mouse testes. In leptotene/zygotene spermatocytes a low level of the 1.4-kb mRNA was observed. Both pol-beta mRNAs were found in meiotic pachytene spermatocytes, with the 1.3-kb form being more abundant. In contrast, the 1.4-kb form was more abundant in haploid round spermatids. Polysome gradient analyses indicated that the two pol-beta mRNAs were predominantly present in the nonpolysomal fractions of spermatocytes. In round spermatids, a larger fraction of the 1.4-kb pol-beta mRNA was associated with polysomes, correlating well with the higher levels of pol-beta enzyme detected during spermiogenesis. The pattern of PADPRP mRNA expression differed from the expression of pol-beta mRNA. The two PADPRP mRNAs of 3.7 and 3.8 kb were present in type A and type B spermatogonia, reached their highest levels in pachytene spermatocytes, and were greatly reduced in haploid round and elongating spermatids. Most of the pachytene spermatocyte PADPRP and mRNAs were present in polysomes, whereas a greater percentage of PADPRP mRNAs in round spermatids were detected in the nonpolysomal fractions. This finding correlates with the immunocytochemical nuclear localization of this enzyme in pachytene spermatocytes. These data demonstrate that different developmental patterns of mRNA expression and translational regulation exist for the pol-beta and PADPRP mRNAs during differentiation of male germinal cells.