XRCC1 and obesity due to melanocortin 4 receptor deficiency: The upregulation of XRCC1 and Ligase III in B-DNA mice on the obesity-inducing diet and H-DNA mice on both diets, compared to B-DNA mice on the CD, further suggests that the repair of obesity- and H-DNA-induced DSBs is carried out through an error-prone MMEJ pathway.