Terminally differentiated muscle cells are defective in base excision DNA repair and hypersensitive to oxygen injury

Abstract

The differentiation of skeletal myoblasts is characterized by permanent withdrawal from the cell cycle and fusion into multinucleated myotubes. Muscle cell survival is critically dependent on the ability of cells to respond to oxidative stress. Base excision repair (BER) is the main repair mechanism of oxidative DNA damage. In this study, we compared the levels of endogenous oxidative DNA damage and BER capacity of mouse proliferating myoblasts and their differentiated counterpart, the myotubes. Changes in the expression of oxidative stress marker genes during differentiation, together with an increase in 8-hydroxyguanine DNA levels in terminally differentiated cells, suggested that reactive oxygen species are produced during this process. The repair of 2-deoxyribonolactone, which is exclusively processed by longpatch BER, was impaired in cell extracts from myotubes. The repair of a natural abasic site (a preferred substrate for short-patch BER) also was delayed. The defect in BER of terminally differentiated muscle cells was ascribed to the nearly complete lack of DNA ligase I and to the strong down-regulation of XRCC1 with subsequent destabilization of DNA ligase III␣. The attenuation of BER in myotubes was associated with significant accumulation of DNA damage as detected by increased DNA single-strand breaks and phosphorylated H2AX nuclear foci upon exposure to hydrogen peroxide. We propose that in skeletal muscle exacerbated by free radical injury, the accumulation of DNA repair intermediates, due to attenuated BER, might contribute to myofiber degeneration as seen in sarcopenia and many muscle disorders.oxidative stress ͉ XRCC1 ͉ DNA ligases ͉ DNA single-strand breaks ͉ 8-oxoguanine

Activities of DNA base excision repair enzymes in liver and brain correlate with body mass, but not lifespan

“…Values are natural log transformations of data from Tables 1 and 4 in brain and liver. Our measurements in these tissues will disproportionately reflect the activities of highly differ- Narciso et al (2007) demonstrated that a significant reduction in BER capacity occurs during differentiation of actively mitotic skeletal muscle progenitors (myoblasts) to post-mitotic myotubes (myofiber-like). Other authors have shown that BER enzyme activities are upregulated at specific times during the cell cycle (Chaudhry 2007) and are generally elevated in tissues containing higher proportions of actively mitotic cells (see Karahalil et al 2002).…”

DNA damage response by single-strand breaks in terminally differentiated muscle cells and the control of muscle integrity

“…The decreased BER capacity of terminally differentiated muscle cells has been shown to lead to accumulation of DNA sSSBs upon oxidative stress. 3 As shown in Figure 1a, DNA SSB also accumulate after exposure to an alkylating agent, namely methyl methanesulfonate (MMS; 1 mM, 30 min), which induces SSB as intermediates during the BER process. To gain insights into the fate of persistent SSB in the genome of post-mitotic muscle cells, cell survival was measured in proliferating and terminally differentiated cells following exposure to MMS and CPT by counting metabolically active cells.…”

“…DNA repair is strongly affected by the exit from the cell cycle as revealed by downregulation of the major DNA repair pathways. 2 This occurs during differentiation-associated gene reprogramming at transcriptional level as in the case of genes coding for proteins shared by DNA repair and replication (e.g., replicative DNA polymerases, Flap structure-specific endonuclease 1, proliferating cell nuclear antigen and DNA ligase 1) 3 or repair proteins that are cell-cycle related (e.g., XRCC1 (X-ray repair complementing defective repair in Chinese hamster cells 1), uracil-DNA glycosylase). 4,5 Alternatively, post-translational modifications may modify the efficiency of specific DNA repair components as in the case of transcription factor II H that, because of reduced ubiquitination, may lead to decreased global genomic nucleotide excision repair typical of differentiated cells.…”

DNA Damage Response and DNA Repair in Skeletal Myocytes From a Mouse Model of Spinal Muscular Atrophy

“…Differentiated myocytes can efficiently activate p53 after DNA damage but these cells possess a downstream blockade of p53-mediated apoptosis and thus evade death (12). Although seminal studies are emerging on DDR and DNA repair mechanisms in differentiated skeletal muscle cells (10)(11)(12)(13), there is limited knowledge on whether myopathy-causing gene mutations can alter DDR and DNA repair mechanisms in skeletal muscle.…”