Yeast Apn2 is an AP endonuclease and DNA 3′-diesterase that belongs to the Exo III family with homology to the E. coli exonuclease III, Schizosaccharomyces pombe eth1, and human AP endonucleases APEX1 and APEX2. In the absence of Apn1, the major AP endonuclease in yeast, Apn2 can cleave the DNA backbone at an AP lesion initiating the base excision repair pathway. To study the role and relative contribution of Apn2, we took advantage of a reporter system that was previously used to delineate how uracil-derived AP sites are repaired. At this reporter, disruption of the Apn1-initiated base excision repair pathway led to a significant elevation of A:T to C:G transversions. Here we show that such highly elevated A:T to C:G transversion mutations associated with uracil residues in DNA are abolished when apn1∆ yeast cells are grown in glucose as the primary carbon source. We also show that the disruption of Apn2, either by the complete gene deletion or by the mutation of a catalytic residue, results in a similarly reduced rate of the uracil-associated mutations. Overall, our results indicate that Apn2 activity is regulated by the glucose repression pathway in yeast.

酵母 Apn2 是一种 AP 核酸内切酶和 DNA 3'-二酯酶，属于 Exo III 家族，与大肠杆菌核酸外切酶 III、粟酒裂殖酵母同源eth1 和人 AP 核酸内切酶 APEX1 和 APEX2。在酵母中主要的 AP 核酸内切酶 Apn1 不存在的情况下，Apn2 可以在 AP 损伤处切割 DNA 骨架，启动碱基切除修复途径。为了研究 Apn2 的作用和相对贡献，我们利用了以前用于描述尿嘧啶衍生 AP 位点修复方式的报告系统。在本报告中，Apn1 启动的碱基切除修复途径的中断导致 A:T 到 C:G 颠换的显着升高。在这里，我们表明，当apn1∆时，与 DNA 中尿嘧啶残基相关的如此高度升高的 A:T酵母细胞在作为主要碳源的葡萄糖中生长。我们还表明，通过完整的基因缺失或催化残基的突变，Apn2 的破坏会导致尿嘧啶相关突变的发生率同样降低。总体而言，我们的结果表明 Apn2 活性受酵母中葡萄糖抑制途径的调节。