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

Abstract

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.

Multiple Feature Selection Strategies Identified Novel Cardiac Gene Expression Signature for Heart Failure

“…HMGN2 regulates active and bivalent genes by promoting an epigenetic landscape of active histone modifications at promoters and enhancers ( Garza-Manero et al, 2019 ). HMGN2 protected corticogenesis via maintaining global chromatin accessibility at promoter regions, thus ensuring proper transcriptome regulation ( Apelt et al, 2020 ; Gao et al, 2020 ). There are few studies to certificate the role of HMGN2 in the progress of HF.…”

SCAI promotes error‐free repair of DNA interstrand crosslinks via the Fanconi anemia pathway

“…UV‐C laser micro‐irradiation was performed essentially as described previously (Apelt et al , 2020). Briefly, U2OS cells stably expressing GFP‐SCAI or transiently transfected with GFP‐Polη were grown on 18‐mm quartz coverslips.…”

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

“…Moreover, this nucleosome binding region was shown to exhibit a highly similar amino acid sequence with the vertebrate HMGN1 protein in its intrinsically disordered RRSARLSA motif 19 . Interestingly, HMGN1 also competes against histone H1 for nucleosome binding sites in a dynamic flux of chromatin remodeling based on cellular context such as development, differentiation, and DNA damage response 24–26 . As a chromosomal architectural transcription factor, HMGN1 is known to affect histone post-translational modifications (PTMs) while activating ATM in response to DNA damage which leads to a more open chromatin state and allows for less sterically hindered access of DNA repair machinery to the site of the lesion.…”

“…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 . Understanding the molecular mechanisms underpinning extremophile tolerance could provide us clues on how human survival in space could be improved through genetic engineering.…”