Biosynthesis of DNA polymerase beta in chick embryonic cells

A monospecific antibody to chick embryo DNA polymerase beta was prepared from a rabbit immunized with the homogeneous enzyme preparation. The antibody has high neutralizing ability to the enzyme activity and, in the presence of formalin fixed Staphylococcus aureus, precipitates a Mr = 40,000 polypeptide from the crude extract and the partially purified DNA polymerase beta which were prepared from [35S]methionine-labeled chick embryonic cells. Pulse-chase experiments were carried out to clarify the process of the biosynthesis of DNA polymerase beta. We have attempted to detect a precursor polypeptide which would be expected to have the following properties: 1) a polypeptide which is specifically precipitated by the antibody and has a molecular weight different from 40,000, 2) the amount of the 35S-labeled polypeptide decreases in the chase period, and 3) 35S-labeled polypeptide which is eliminated from the immunoprecipitate by adding an excess amount of purified unlabeled DNA polymerase beta. However, no such polypeptide was detected in the 30-min pulse-labeled cells. A Mr = 40,000 polypeptide was immunoprecipitated from the extract of 30-min pulse-labeled cells and its amount did not change in a 5-hr chase, then decreased. Results suggest that a Mr = 40,000 polypeptide of chick embryo DNA polymerase beta is the initial translation product of the mRNA of DNA polymerase beta.