We have fractionated homogenates of Chinese hamster cells grown in tissue culture, and found that >80% of those cells' DNA-dependent DNA polymerase appears localized in the soluble cytoplasm. The Chinese hamster cytoplasmic DNA polymerase is very similar to DNA polymerases from several mammalian sources: it is large and heterogeneous (165,000-200,000 daltons), sensitive to sulfhydryl-blocking reagents and absolutely requires double stranded templates containing free 3′-OH primers. Two distinct species of DNA polymerase also have been isolated from purified Chinese hamster nuclei. One nuclear DNA polymerase appeared to be identical to DNA polymerase found in the cells' soluble cytoplasm. The second polymerase, comprising 1.5-3% of the total DNA polymerase activity, was found only in nuclear extracts. That enzyme is resistant to sulfhydryl-blocking reagents and has an apparent molecular weight of 49,000. The data discussed in this report suggest that Chinese hamster cells, like other mammalian cell types, possess at least two DNA-dependent DNA polymerases that might participate in replicative DNA biosynthesis.
ASJC Scopus subject areas
- Molecular Biology