Differential expression of DNA polymerase α in normal and transformed human fibroblasts

The expression of DNA polymerase α (pol α) was studied in human fibroblast lines WI38 (fetal lung) and GM3529 (skin, established from a 66 yr old donor), and their Simian virus 40 (SV40) large tumor antigen (TAg)-transformed corollaries, 2RA and 2-1 respectively. Both SV40-transformed and pSV3.neo (SV40-derived plasmid)-transformed cells express TAg, a virally encoded protein not expressed by the normal parent cell lines. Northern blot hybridization studies showed increased recovery of pol α mRNA from transformed cells compared with normal cells. This increase was correlated with increased pol α mRNA transcription as determined by nuclear run-on assays. Northern blot analyses also showed an increase in the instability of translationally active pol α mRNA in transformed cells. The results suggest that TAg, in addition to its dsDNA binding, pol α binding, retinoblastoma protein binding and helicase activities, may be involved either directly or indirectly in regulation of the steady state mRNA levels of pol α at the transcriptional level in both fetal and aged donor-derived transformed fibroblasts.