Giot L, Chanet R, Simon M, Facca C, Faye G
Institut Curie-Biologie, Centre Universitaire, Orsay, France.
Genetics. 1997 Aug;146(4):1239-51. doi: 10.1093/genetics/146.4.1239.
The POL3 encoded catalytic subunit of DNA polymerase delta possesses a highly conserved C-terminal cysteine-rich domain in Saccharomyces cerevisiae. Mutations in some of its cysteine codons display a lethal phenotype, which demonstrates an essential function of this domain. The thermosensitive mutant pol3-13, in which a serine replaces a cysteine of this domain, exhibits a range of defects in DNA repair, such as hypersensitivity to different DNA-damaging agents and deficiency for induced mutagenesis and for recombination. These phenotypes are observed at 24 degrees, a temperature at which DNA replication is almost normal; this differentiates the functions of POL3 in DNA repair and DNA replication. Since spontaneous mutagenesis and spontaneous recombination are efficient in pol3-13, we propose that POL3 plays an important role in DNA repair after irradiation, particularly in the error-prone and recombinational pathways. Extragenic suppressors of pol3-13 are allelic to sdp5-1, previously identified as an extragenic suppressor of pol3-11. SDP5, which is identical to HYS2, encodes a protein homologous to the p50 subunit of bovine and human DNA polymerase delta. SDP5 is most probably the p55 subunit of Pol delta of S. cerevisiae and seems to be associated with the catalytic subunit for both DNA replication and DNA repair.
在酿酒酵母中，DNA聚合酶δ的催化亚基POL3编码一个高度保守的C端富含半胱氨酸结构域。其部分半胱氨酸密码子发生突变会表现出致死表型，这表明该结构域具有重要功能。温度敏感型突变体pol3-13中，该结构域的一个半胱氨酸被丝氨酸取代，在DNA修复方面表现出一系列缺陷，比如对不同DNA损伤剂高度敏感，诱导突变和重组功能缺失。这些表型在24摄氏度时就能观察到，此时DNA复制基本正常；这区分了POL3在DNA修复和DNA复制中的功能。由于pol3-13中自发突变和自发重组效率较高，我们认为POL3在辐射后的DNA修复中发挥重要作用，尤其是在易错和重组途径中。pol3-13的基因外抑制子与sdp5-1等位，sdp5-1之前被鉴定为pol3-11的基因外抑制子。SDP5与HYS2相同，编码一种与牛和人DNA聚合酶δ的p50亚基同源的蛋白质。SDP5很可能是酿酒酵母Pol δ的p55亚基，似乎在DNA复制和DNA修复过程中都与催化亚基相关。
