PHOSPHORYLATION OF THE DNA-POLYMERASE ALPHA-PRIMASE-B SUBUNIT IS DEPENDENT ON ITS ASSOCIATION WITH THE P180 POLYPEPTIDE

The B subunit of the DNA polymerase (pol) alpha-primase complex execut es an essential role at the initial stage of DNA replication in Saccha romyces cerevisiae and is phosphorylated in a cell cycle-dependent man ner. In this report, we show that the four subunits of the yeast DNA p olymerase alpha-primase complex are assembled throughout the cell cycl e, and physical association between newly synthesized pol alpha (p180) and unphosphorylated B subunit (p86) occurs very rapidly, Therefore, B subunit phosphorylation does not appear to modulate p180 . p86 inter action, Conversely, by depletion experiments and by using a yeast muta nt strain, which produces a low and constitutive level of the p180 pol ypeptide, we found that formation of the p180 p86 subcomplex is requir ed for B subunit phosphorylation.