Difference in the expression level of DNA polymerase β among mouse tissues: High expression in the pachytene spermatocyte

Abstract

The expression level of DNA polymerase β was determined in various mouse tissues. Northern blot hybridization analysis using rat cDNA as a probe revealed that the mRNA of about 1.5 kb for this enzyme is present in all kinds of tissues examined, but its content widely varies among tissues; the most abundant DNA polymerase β mRNA was present in the testis, which was followed by brain, thymus, and spleen. The mRNA content was low in heart, kidney, and liver. In testis and brain, two minor species of transcripts of 3.3 and 6.2 kb were detected in addition to that of 1.5 kb. DNA polymerase β activities in these tissues were closely correlated with the mRNA content, indicating that the expression of this enzyme is mainly regulated by the level of the mRNA. A survey of DNA polymerase β mRNA levels in the testes at successive postnatal developmental stages and in isolated spermatogenic cells indicated that DNA polymerase β mRNA was most abundant in spermatocytes at early pachytene. Since meiotic recombination occurs in this period, DNA polymerase β may be involved in the repair-type DNA synthesis associated with the recombination process.