Budd M E, Wittrup K D, Bailey J E, Campbell J L
Division of Chemistry, California Institute of Technology, Pasadena 91125.
Mol Cell Biol. 1989 Feb;9(2):365-76. doi: 10.1128/mcb.9.2.365-376.1989.
We have used a set of seven temperature-sensitive mutants in the DNA polymerase I gene of Saccharomyces cerevisiae to investigate the role of DNA polymerase I in various aspects of DNA synthesis in vivo. Previously, we showed that DNA polymerase I is required for mitotic DNA replication. Here we extend our studies to several stages of meiosis and repair of X-ray-induced damage. We find that sporulation is blocked in all of the DNA polymerase temperature-sensitive mutants and that premeiotic DNA replication does not occur. Commitment to meiotic recombination is only 2% of wild-type levels. Thus, DNA polymerase I is essential for these steps. However, repair of X-ray-induced single-strand breaks is not defective in the DNA polymerase temperature-sensitive mutants, and DNA polymerase I is therefore not essential for repair of such lesions. These results suggest that DNA polymerase II or III or both, the two other nuclear yeast DNA polymerases for which roles have not yet been established, carry out repair in the absence of DNA polymerase I, but that DNA polymerase II and III cannot compensate for loss of DNA polymerase I in meiotic replication and recombination. These results do not, however, rule out essential roles for DNA polymerase II or III or both in addition to that for DNA polymerase I.
我们利用酿酒酵母DNA聚合酶I基因中的一组七个温度敏感突变体，来研究DNA聚合酶I在体内DNA合成各个方面的作用。此前，我们表明有丝分裂DNA复制需要DNA聚合酶I。在此，我们将研究扩展到减数分裂的几个阶段以及X射线诱导损伤的修复。我们发现，在所有DNA聚合酶温度敏感突变体中孢子形成均受阻，且减数分裂前的DNA复制不发生。减数分裂重组的发生率仅为野生型水平的2%。因此，DNA聚合酶I对于这些步骤至关重要。然而，DNA聚合酶温度敏感突变体中X射线诱导的单链断裂修复并无缺陷，因此DNA聚合酶I对于此类损伤的修复并非必不可少。这些结果表明，另外两种尚未明确其作用的核酵母DNA聚合酶——DNA聚合酶II或III，或两者共同作用，在没有DNA聚合酶I的情况下进行修复，但DNA聚合酶II和III无法弥补减数分裂复制和重组中DNA聚合酶I的缺失。然而，这些结果并不排除DNA聚合酶II或III或两者除了在DNA聚合酶I的作用之外还具有重要作用。
