Transcription-coupled repair (TCR) removes DNA lesions from the transcribed strand of active genes. Stalling of RNA polymerase II (RNAPII) at DNA lesions initiates TCR through the recruitment of the CSB and CSA proteins. The full repertoire of proteins required for human TCR – particularly in a chromatin context - remains to be determined. Studies in mice have revealed that the nucleosome-binding protein HMGN1 is required to enhance the repair of UV-induced lesions in transcribed genes. However, whether HMGN1 is required for human TCR remains unaddressed. Here, we show that knockout or knockdown of HMGN1, either alone or in combination with HMGN2, does not render human cells sensitive to UV light or Illudin S-induced transcription-blocking DNA lesions. Moreover, transcription restart after UV irradiation was not impaired in HMGN-deficient cells. In contrast, TCR-deficient cells were highly sensitive to DNA damage and failed to restart transcription. Furthermore, GFP-tagged HMGN1 was not recruited to sites of UV-induced DNA damage under conditions where GFP-CSB readily accumulated. In line with this, HMGN1 did not associate with the TCR complex, nor did TCR proteins require HMGN1 to associate with DNA damage-stalled RNAPII. Together, our findings suggest that HMGN1 and HMGN2 are not required for human TCR.

转录偶联修复（TCR）可从活性基因的转录链中去除DNA损伤。DNA损伤处的RNA聚合酶II（RNAPII）失速可通过募集CSB和CSA蛋白来启动TCR。人类TCR所需的全部蛋白质，特别是在染色质的背景下，仍有待确定。小鼠研究表明，核小体结合蛋白HMGN1是增强转录基因中紫外线诱导的损伤修复的必需物质。但是，人类TCR是否需要HMGN1仍未解决。在这里，我们显示单独或与HMGN2组合使用的HMGN1的敲除或敲除不会使人细胞对紫外线或Illudin S诱导的转录阻滞DNA损伤敏感。而且，在HMGN缺陷的细胞中，紫外线照射后的转录重新启动不受影响。相反，缺乏TCR的细胞对DNA损伤高度敏感，无法重新启动转录。此外，在GFP-CSB容易积聚的条件下，没有将GFP标记的HMGN1募集到紫外线诱导的DNA损伤位点。与此相符，HMGN1不与TCR复合体缔合，TCR蛋白也不需要HMGN1与DNA破坏的RNAPII缔合。在一起，我们的发现表明，人类TCR不需要HMGN1和HMGN2。