Previously, we found that two isoforms of the ZNF268 gene (ZNF268a and ZNF268b2, with and without the KRAB domain, respectively) might play distinct roles in normal epithelia and in cervical cancer. Here we further investigated that KRAB domain defined the function disparity in part by reinforcing nuclear localization of ZNF268a. We found that the A-box of KRAB alone retained major specific nuclear localization activity. In contrast, the B-box alone did not have nuclear localization activity but enhanced it significantly. Consistent with the critical function of the A-box, each mutation of six conserved residues (V9, V11, F13, E16, E17 and W18) in the A-box dramatically impaired nuclear localization activity. Furthermore, the unique nuclear localization activity of KRAB was verified in seven additional KRAB-containing zinc finger proteins (KRAB-ZFPs), suggesting that it is a universal feature of KRAB-ZFPs. Finally, KRAB exerted its unique nuclear localization activity by interacting with the RBCC domain of its corepressor KAP1. Our results have revealed a novel mechanism by which the KRAB domain reinforces nuclear localization of KRAB-ZFPs by interacting with KAP1. Our study also suggests that loss of the KRAB domain in KRAB-ZFPs due to aberrant alternative splicing might contribute to carcinogenesis.

中文翻译：

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KRAB 结构域的新活性可通过与 KAP1 相互作用来增强含 KRAB 的锌指蛋白的核定位。


此前，我们发现ZNF268基因的两种亚型（ZNF268a和ZNF268b2，分别具有和不具有KRAB结构域）可能在正常上皮和宫颈癌中发挥不同的作用。在这里，我们进一步研究了 KRAB 结构域通过增强 ZNF268a 的核定位来部分定义功能差异。我们发现 KRAB 的 A 盒单独保留了主要的特异性核定位活性。相比之下，单独的 B-box 不具有核定位活性，但显着增强了其核定位活性。与 A 盒的关键功能一致，A 盒中六个保守残基（V9、V11、F13、E16、E17 和 W18）的每次突变都会显着损害核定位活性。此外，KRAB 独特的核定位活性在另外 7 个含 KRAB 的锌指蛋白 (KRAB-ZFP) 中得到了验证，表明它是 KRAB-ZFP 的普遍特征。最后，KRAB 通过与其辅阻遏物 KAP1 的 RBCC 结构域相互作用，发挥其独特的核定位活性。我们的结果揭示了一种新机制，KRAB 结构域通过与 KAP1 相互作用来增强 KRAB-ZFP 的核定位。我们的研究还表明，由于异常选择性剪接而导致 KRAB-ZFP 中 KRAB 结构域的丢失可能会导致致癌。