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

Abstract:

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 alpha, beta, delta, epsilon, and zeta. The resting B cells did not express polymerases alpha or epsilon at detectable levels, although they did express polymerases beta, delta, and zeta. Thus, polymerase epsilon, as well as alpha, appears to have a primary role in chromosomal replication of murine B lymphocytes. Further, the lack of expression of polymerase epsilon in resting cells indicates that this enzyme is not used in any DNA repair pathways by these cells. The expression of polymerase zeta 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.

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