Cohesin promotes the repair of ionizing radiation-induced DNA double-strand breaks in replicated chromatin

Abstract

The cohesin protein complex holds sister chromatids together after synthesis until mitosis. It also contributes to post-replicative DNA repair in yeast and higher eukaryotes and accumulates at sites of laser-induced damage in human cells. Our goal was to determine whether the cohesin subunits SMC1 and Rad21 contribute to DNA double-strand break repair in X-irradiated human cells in the G2 phase of the cell cycle. RNA interference-mediated depletion of SMC1 sensitized HeLa cells to X-rays. Repair of radiation-induced DNA double-strand breaks, measured by γH2AX/53BP1 foci analysis, was slower in SMC1- or Rad21-depleted cells than in controls in G2 but not in G1. Inhibition of the DNA damage kinase DNA-PK, but not ATM, further inhibited foci loss in cohesin-depleted cells in G2. SMC1 depletion had no effect on DNA single-strand break repair in either G1 or late S/G2. Rad21 and SMC1 were recruited to sites of X-ray-induced DNA damage in G2-phase cells, but not in G1, and only when DNA damage was concentrated in subnuclear stripes, generated by partially shielded ultrasoft X-rays. Our results suggest that the cohesin complex contributes to cell survival by promoting the repair of radiation-induced DNA double-strand breaks in G2-phase cells in an ATM-dependent pathway.

The Sister Chromatid Cohesion Pathway Suppresses Multiple Chromosome Gain and Chromosome Amplification

“…Cohesin is also important for gene expression and DNA repair (Sjogren and Nasmyth 2001;Kim et al 2002a, b;Unal et al 2004;Bauerschmidt et al 2010;Wu et al 2012).…”

RAD21 cohesin overexpression is a prognostic and predictive marker exacerbating poor prognosis in kras mutant colorectal carcinomas

“…To date, both in vitro and in vivo data demonstrate that RAD21 expression influences cellular sensitivity to DNA-damaging agents such as those used in chemotherapy or chemoradiotherapy (Atienza et al, 2005;Bauerschmidt et al, 2010;Xu et al, 2010;Xu et al, 2011a, b). An increased susceptibility of cancer cell lines to conventional chemotherapeutics was demonstrated following knockdown of RAD21 or other cohesin gene (Atienza et al, 2005;Xu et al, 2011b;Supernat et al, 2012).…”

“…An increased susceptibility of cancer cell lines to conventional chemotherapeutics was demonstrated following knockdown of RAD21 or other cohesin gene (Atienza et al, 2005;Xu et al, 2011b;Supernat et al, 2012). Similarly, yeast mutants and mammalian cells with reduced functional RAD21 have also been shown to have increased sensitivity to ionising radiation secondary to deficiency in the repair of DNA double-stranded breaks (Birkenbihl and Subramani, 1992;Bauerschmidt et al, 2010;Xu et al, 2010). In vitro, we have further verified the effect of RAD21 depletion within a CRC cell line to the sensitivity of commonly used CRC chemotherapeutics.…”

“…During the G1 phases of the cell cycle, the cohesin complex is thought to form a ring and entrap DNA helices and, with the aid of several accessory and regulatory proteins, facilitates binding of newly formed sister chromosomes and appropriate chromosome segregation during anaphase (Haering et al, 2008). The cohesin complex is also implicated in several other important processes including homologous recombinational repair or DNA damage (Birkenbihl and Subramani, 1992;Nasmyth et al, 2001;Sonoda et al, 2001;Watrin and Peters, 2006), in particular double-stranded breaks (Birkenbihl and Subramani, 1992;Bauerschmidt et al, 2010;Xu et al, 2010), cell cycle checkpoint control (Watrin and Peters, 2009), chromatin remodelling (Hakimi et al, 2002), gene regulation (Supernat et al, 2012) and prevention of read-through transcription. Presence of this versatile complex in subcellular locations outside the nucleus and within extracellular matrix has also been observed; however, the exact purpose of cohesin in these instances is unknown.…”

The Relationship Between Homologous Recombination Repair and the Sensitivity of Human Epidermis to the Size of Daily Doses Over a 5-Week Course of Breast Radiotherapy

“…NHEJ is an error prone method of repair although homologous recombination has a high fidelity for repair that is independent of DNA damage levels (fraction size; 7). Another mechanism contributing to loss of fraction size sensitivity in S/G2 could be via cohesin, which facilitates more efficient DSB repair in replicated chromatin (29) and may enhance correct DSB repair at high doses in S/G2 in an homologous recombination-independent manner (13). The tightly bound chromatid in S/G2 might serve as a scaffold to hold break ends in place and thus avoid loss or rearrangement of chromosome material.…”