Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia.
Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia.
Int J Mol Sci. 2021 Apr 28;22(9):4679. doi: 10.3390/ijms22094679.
Poly(ADP-ribose) polymerase 2 (PARP2) participates in base excision repair (BER) alongside PARP1, but its functions are still under study. Here, we characterize binding affinities of PARP2 for other BER proteins (PARP1, APE1, Polβ, and XRCC1) and oligomerization states of the homo- and hetero-associated complexes using fluorescence-based and light scattering techniques. To compare PARP2 and PARP1 in the efficiency of PAR synthesis, in the absence and presence of protein partners, the size of PARP2 PARylated in various reaction conditions was measured. Unlike PARP1, PARP2 forms more dynamic complexes with common protein partners, and their stability is effectively modulated by DNA intermediates. Apparent binding affinity constants determined for homo- and hetero-oligomerized PARP1 and PARP2 provide evidence that the major form of PARP2 at excessive PARP1 level is their heterocomplex. Autoregulation of PAR elongation at high PARP and NAD concentrations is stronger for PARP2 than for PARP1, and the activity of PARP2 is more effectively inhibited by XRCC1. Moreover, the activity of both PARP1 and PARP2 is suppressed upon their heteroPARylation. Taken together, our findings suggest that PARP2 can function differently in BER, promoting XRCC1-dependent repair (similarly to PARP1) or an alternative XRCC1-independent mechanism via hetero-oligomerization with PARP1.
聚（ADP-核糖）聚合酶 2（PARP2）与 PARP1 一起参与碱基切除修复（BER），但其功能仍在研究中。在这里，我们使用荧光和光散射技术来描述 PARP2 与其他 BER 蛋白（PARP1、APE1、Polβ 和 XRCC1）的结合亲和力和同型和异型相关复合物的寡聚状态。为了比较 PARP2 和 PARP1 在 PAR 合成效率方面的差异，在没有和存在蛋白伴侣的情况下，测量了在各种反应条件下 PARP2 聚 PAR 的大小。与 PARP1 不同，PARP2 与常见的蛋白伴侣形成更动态的复合物，并且它们的稳定性可以通过 DNA 中间体有效地调节。对同型和异型寡聚化的 PARP1 和 PARP2 确定的表观结合亲和力常数提供了证据，即在过量 PARP1 水平下 PARP2 的主要形式是其异源复合物。在高 PARP 和 NAD 浓度下，PARP2 对 PAR 延伸的自动调节要强于 PARP1，并且 XRCC1 更有效地抑制 PARP2 的活性。此外，PARP1 和 PARP2 的活性都在其异源 PAR 化后受到抑制。总之，我们的研究结果表明，PARP2 在 BER 中可以发挥不同的作用，通过与 PARP1 的异源寡聚化促进 XRCC1 依赖性修复（与 PARP1 相似）或通过替代的 XRCC1 非依赖性机制。
