Gene expression misregulation in DNA repair deficient cells

MUÑOZ, JUAN C.; BECKERMAN, INÉS; BOUVIER, LEÓN A.; MUÑOZ, MANUEL J.

Virtual

Congreso; REUNIÓN DE SOCIEDADES DE BIOCIENCIAS 2021-LXVI REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2021

DNA damage caused naturally by UV light exposure in skin cells triggers not only lesion repair mechanisms but also a global gene expression response that includes RNAPII degradation. Recent identification of the lysine residue responsible for RNAPII ubiquitination and degradation uncovered an unanticipated relevance for RNAPII levels in the control of gene expression in UV-treated cells.Since DNA is the only biopolymer that is neither disposable nor recyclable, it must be repaired when damaged. Among the various repair systems that human cells have, the nucleotide excision repair (NER) system is the one that deals with most of UV light-induced lesions. Damage detection by NER system occurs by two different DNA-sensing mechanisms that then converge on the same machinery that repairs the damage: transcription-coupled repair (TC-NER) and global genome repair (GG-NER). The ?last resort? model states that a RNAPII molecule stalled in front of a UV-induced DNA lesion is degraded so as to allow access to the repair machinery and, therefore, RNAPII degradation would be part of the TC-NER system. However, different evidences suggest that the scenario could be different. On the one hand, most of the repair of lesions in template strands in transcriptionally active genes, the only lesions repaired by TC-NER, occurs in the first hours post UV, while degradation of RNAPII is observed hours later. On the other hand, preliminary results from our group show that RNAPII degradation is mainly controlled by the GG-NER system. Using the CRISPR/Cas9 editing system, we generated human keratinocytes unable to recognize lesions through the GG-NER system (GG-NER KO / TC-NER WT cells) and observed a marked inhibition in the degradation of RNAPII in response to UV light. Moreover, impairment of the actual lesion-repair, but its lesion recognition, enhanced RNAPII degradation. While in GG-NER KO cells we observed less RNAPII degradation and enhanced cell viability upon UV, in comparison to wild type keratinocytes, in different lesion-repair mutant cells we observed the opposite: enhanced RNAPII degradation and reduced cell viability upon UV. Consequently, we propose that RNAPII levels determine cell viability and are mainly controlled by an unexplored GG-NER-dependent mechanism.