Bouvier D, De Recondo A M, Baldacci G
C.N.R.S.-U.P.R. 272-Institute for Cancer Research, Villejuif, France.
Exp Cell Res. 1993 Jul;207(1):41-7. doi: 10.1006/excr.1993.1160.
We studied the phosphorylation of fission yeast p170 (the catalytic subunit of DNA polymerase alpha) and its relationship to the cell cycle. In exponentially growing cells, p170 was phosphorylated at serine residues. Its phosphorylation level did not quantitatively change when cell strains carrying conditional cell division cycle (cdc) mutations arrested at different stages of the cell cycle, under restrictive growth conditions. Especially, phosphorylation did not significantly vary when cells carrying the temperature-sensitive cdc2-33 mutation were shifted to the restrictive temperature, which indicates a minor role, if any, of p34cdc2 in this process. Also, the extent of p170 phosphorylation did not remarkably change during mitosis, a situation which differs from that reported for human DNA polymerase alpha. We used immunofluorescence microscopy and cell fractionation to study the intracellular distribution of p170. We here provide evidence that the protein remains tenaciously associated with nuclear structures throughout the cell cycle and is not redistributed into the cytoplasm at mitosis, as it is in human cells. A possible correlation between phosphorylation, nuclear binding, and mitotic behavior of DNA polymerase alpha catalytic subunits in eukaryotes is therefore conceivable.
我们研究了裂殖酵母p170（DNA聚合酶α的催化亚基）的磷酸化及其与细胞周期的关系。在指数生长的细胞中，p170在丝氨酸残基处被磷酸化。在限制性生长条件下，携带条件性细胞分裂周期（cdc）突变的细胞株在细胞周期的不同阶段停滞时，其磷酸化水平没有定量变化。特别是，携带温度敏感型cdc2 - 33突变的细胞转移到限制性温度时，磷酸化没有显著变化，这表明p34cdc2在这个过程中即使有作用也是次要的。此外，在有丝分裂期间p170的磷酸化程度也没有明显变化，这种情况与人类DNA聚合酶α的报道不同。我们使用免疫荧光显微镜和细胞分级分离来研究p170的细胞内分布。我们在此提供证据表明，该蛋白在整个细胞周期中都与核结构紧密结合，并且在有丝分裂时不会像在人类细胞中那样重新分布到细胞质中。因此，可以想象真核生物中DNA聚合酶α催化亚基的磷酸化、核结合和有丝分裂行为之间可能存在相关性。
