The abasic site is one the most common DNA lesions formed in cells; it induces a severe blockage of DNA replication and is highly mutagenic. We continue to use Gp90 exo^–, the sole DNA polymerase from Pseudomonas aeruginosa phage PaP1, to study DNA replication upon encountering an abasic site lesion. Gp90 exo^– can incorporate dNTPs opposite the abasic site, but extension past this site is extremely slow. Among the four dNTPs, dATP is preferentially incorporated opposite the abasic site, consistent with the A-rule. The incorporation is independent of the identity of the nucleotide 5′ of the abasic site. The incorporation of dATP opposite the abasic site occurs by direct incorporation of dNTP opposite the abasic site without a −1 frameshift deletion. Extension from an A:abasic site pair by Gp90 exo^– is slightly unfavorable relative to those from other abasic site pairs. Incorporation of dATP opposite the abasic site is preferential and shows a biphasic shape, indicating that this incorporation is much faster than the subsequent dissociation of the polymerase from DNA. The template sequence does not affect the dATP incorporation priority, burst amplitude, burst rate, or dATP dissociation constant. Surface plasmon resonance shows that the presence of an abasic site in the template weakens the binding affinity of Gp90 exo^– to DNA in a binary or ternary complex in the presence of any one kind of dNTP. This study reveals that Gp90 exo^– preferentially inserts A opposite an abasic site via the A-rule, like other DNA polymerases (e.g., Pol θ, KlenTaq, KF exo^–, Pols α, δ/PCNA, and Thermococcus litoralis Pol Vent (exo^–)), providing further insight into DNA replication mediated by P. aeruginosa phage PaP1 upon encountering an abasic site lesion.

中文翻译：

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铜绿假单胞菌噬菌体PaP1的DNA聚合酶通过A规则绕过无碱基位点。

无碱基位点是细胞中最常见的DNA损伤之一。它会严重阻碍DNA复制，并且具有高度的诱变性。我们继续使用Gp90 exo ^–来自铜绿假单胞菌噬菌体PaP1的唯一DNA聚合酶，研究遇到无碱基位点病变时的DNA复制。GP90 EXO ^–可以在无碱基位点对面并入dNTP，但是扩展到该位点的速度非常慢。在这四个dNTP中，与A规则一致，dATP优先结合在无碱基位点对面。掺入与无碱基位点的核苷酸5'的身份无关。与无碱基位点相对的dATP的掺入是通过与无碱基位点相对的dNTP的直接掺入而没有-1移码缺失。Gp90 exo从A：abasic网站对扩展^–相对于其他无碱基位点对而言，这是不利的。相对于无碱基位点的dATP的掺入是优先的，并表现出双相形状，表明这种掺入比随后的聚合酶从DNA上解离要快得多。模板序列不影响dATP掺入优先级，猝发幅度，猝发速率或dATP解离常数。表面等离振子共振表明，在任何一种dNTP存在下，模板中无碱基位点的存在都会削弱Gp90 exo ^–与二元或三元复合物中的DNA的结合亲和力。这项研究表明，Gp90 exo ^–像其他DNA聚合酶（例如Polθ，KlenTaq，KF exo ^–，polsα，δ/ PCNA和litorcoccus litoralis Pol Vent（exo ^–）），可进一步了解由铜绿假单胞菌噬菌体PaP1介导的无碱基位病变引起的DNA复制。