The function of cux1 in oxidative dna damage repair is needed to prevent premature senescence of mouse embryo fibroblasts

Abstract

Despite having long telomeres, mouse embryo fibroblasts (MEFs) senesce more rapidly than human diploid fibroblasts because of the accumulation of oxidative DNA damage. The CUX1 homeodomain protein was recently found to prevent senescence in RAS-driven cancer cells that produce elevated levels of reactive-oxygen species. Here we show that Cux1−/− MEFs are unable to proliferate in atmospheric (20%) oxygen although they can proliferate normally in physiological (3%) oxygen levels. CUX1 contains three domains called Cut repeats. Structure/function analysis established that a single Cut repeat domain can stimulate the DNA binding, Schiff-base formation, glycosylase and AP-lyase activities of 8-oxoguanine DNA glycosylase 1, OGG1. Strikingly and in contrast to previous reports, OGG1 exhibits efficient AP-lyase activity in the presence of a Cut repeat. Repair of oxidative DNA damage and proliferation in 20% oxygen were both rescued in Cux1−/− MEFs by ectopic expression of CUX1 or of a recombinant Cut repeat protein that stimulates OGG1 but is devoid of transcription activation potential. These findings reinforce the causal link between oxidative DNA damage and cellular senescence and suggest that the role of CUX1 as an accessory factor in DNA repair will be critical in physiological situations that generate higher levels of reactive oxygen species.

CUX2 Protein Functions as an Accessory Factor in the Repair of Oxidative DNA Damage

“…5D, lane 11). Similar observations were previously made with the Cut repeats of CUX1 (52). These findings suggest that the mechanism by which Cut repeats stimulate OGG1 may involve a transient interaction between the two proteins.…”

“…D, EMSA was performed using oligonucleotides containing an 8-oxoG and purified hOGG1 in the presence or absence of a CUX1 peptide as indicated. Similar experimental evidence previously established the role of CUX1 in base excision repair (52). Following duplication of the ancestral CUX gene, CUX1 and CUX2 have evolved distinct patterns of gene expression and acquired unique molecular functions.…”

“…Cut repeats were originally characterized as domains that bind to DNA in cooperation with one another or with the Cut homeodomain (50,51). More recently, Cut repeats of CUX1 were shown to bind to OGG1 and stimulate both its glycosylase and AP lyase enzymatic activities (52,53). Knockdown or genetic inactivation of CUX1 was found to delay the repair of oxidative DNA damage, whereas higher CUX1 expression accelerated DNA repair.…”

“…Interestingly, this effect on OGG1 did not require that the Cut repeat protein itself form a stable complex with DNA (52). To test whether the Cut repeats from CUX2 have the same effect on OGG1, we performed EMSAs using oligonucleotides that contain an 8-oxoG.…”

HOXC10 Expression Supports the Development of Chemotherapy Resistance by Fine Tuning DNA Repair in Breast Cancer Cells

“…Several homeodomain related proteins have been functionally related to DNA damage repair (1, 2, 30, 31). Overexpression of HOXA5 in S. cerevisiae up-regulates components of the mismatch repair (MMR) system, important for the detection and repair of DNA damage (32).…”