Human HMGN1 and HMGN2 are not required for transcription-coupled DNA repair

Abstract

Running title: HMGN1 is not involved in TCR * Corresponding author: Martijn Luijsterburg (m.luijsterburg@lumc.nl) 2 Apelt et al. Human HMGN1 and HMGN2 are not required for TCR SummaryTranscription-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 were 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 damagestalled RNAPII. Together, our findings suggest that HMGN1 and HMGN2 are not required for human TCR.

Multi-omics Analysis of Dsup Expressing Human Cells Reveals Open Chromatin Architectural Dynamics Underyling Radioprotection

“…It is also possible that Dsup may act functionally similar to HMGN in terms of enhancing DNA repair mechanisms in addition to its shielding effect 19 , but there is no functional genomics data to yet verify this hypothesis. Indeed, the HMGN proteins colocalize with epigenetic marks of active chromatin, but also promote chromatin decompaction via competitively binding with H1, perhaps similar to how Dsup interacts with nucleosomes 19,24,25,26 .…”

Site-specific modification and segmental isotope labelling of HMGN1 reveals long-range conformational perturbations caused by posttranslational modifications

“…[12][13][14][15][16] Although the precise mechanisms by which HMGN proteins modulate epigenetic processes are still not clear, several studies indicate that these nucleosomal proteins regulate cell-typespecific gene expression, and therefore have potential implications in developmental processes and disease. 11 For example, HMGN proteins have been reported to function as alarmins, [17][18][19] to have both pro- 20 and anti-tumour 21 activities and to have roles in DNA repair, 22,23 immune regulation 17 and Down syndrome. 11,24 These studies, amongst others, highlight the need to understand the molecular-level interactions of HMGN1.…”