Differential expression of DNA polymerase ε in resting and activated B lymphocytes is consistent with an in vivo role in replication and not repair

DNA polymerases may be differentially expressed by cells during periods of quiescence and proliferation. Murine B cells are an ideal population to study because their division time varies widely in vivo, and different subsets can be easily isolated. Consequently, we analyzed RNA from resting cells (B220⁺ peanut agglutinin^-) and activated germinal center cells (B220⁺ peanut agglutinin⁺) from spleens by reverse transcriptase-PCR using primers for five nuclear polymerases and their associated subunits. Gel analyses of the amplified products showed that the rapidly-dividing germinal center B cells expressed DNA polymerases α, β, δ, ε, and ζ. The resting B cells did not express polymerases α or ε at detectable levels, although they did express polymerases β, δ, and ζ. Thus, polymerase ε, as well as α, appears to have a primary role in chromosomal replication of murine B lymphocytes. Further, the lack of expression of polymerase ε in resting cells indicates that this enzyme is not used in any DNA repair pathways by these cells. The expression of polymerase ζ by resting cells suggests that it has another role in DNA repair, perhaps recombination, in addition to its function of bypassing damage during chromosomal replication. Published by Elsevier Science Ltd.