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

The expression of DNA polymerase alpha (pol alpha) was studied in human fibroblast lines W138 (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 alpha mRNA from transformed cells compared with normal cells. This increase was correlated with increased pol alpha mRNA transcription as determined by nuclear run-on assays. Northern blot analyses also showed an increase in the instability of translationally active pol alpha mRNA in transformed cells. The results suggest that TAg, in addition to its dsDNA binding, pol alpha binding, retinoblastoma protein binding and helicase activities, may be involved either directly or indirectly in regulation of the steady state mRNA levels of pol alpha at the transcriptional level in both fetal and aged donor-derived transformed fibroblasts.