Cdc7, Rad53 and Asf1 stabilize Rad52 binding to replicative DNA damage

Abstract

Póster presentado en AbCam Meeting >Mechanism of Recombination: 50th Anniversary Meeting of the Holliday Model>, celebrado en Alicante del 19 al 23 de mayo de 2014The response to DNA lesions that impair the advance of replication forks relies on DNA damage tolerance (DDT) mechanisms, which facilitate fork bypass across the lesions and repair of the ssDNA fragments generated during this process. One of these mechanisms is Homologous Recombination (HR), which uses the information of an intact template to repair DNA breaks. We have recently shown that the recombination proteins Rad52 and Rad51 contribute to tolerate replicative DNA damage through replicative and repair activities, which are regulated during the cell cycle. In S phase, Rad52 and Rad51 travel with the fork and facilitate replication bypass across the lesion by unknown mechanisms. Repriming of DNA synthesis downstream of the lesion leaves Rad52 and Rad51 loaded at the ssDNA lesions left behind the fork, which are repaired at HR centers formed in G2/M (González-Prieto et al. 2013, EMBO J 32:1307). Here, we report a role for the kinase Cdc7 in promoting the loading/stabilization of Rad52 to the ssDNA lesions generated upon treatment with the alkylating agent methyl-methane sulfonate (MMS). This effect is partially mediated by phosphorylation of Mcm2. In addition, we show that Rad53, which requires the kinase activity of Cdc7 for full activation, is also required for Rad52 binding to DNA damage. Notably, Mec1 does not share this function. In addition, we have observed that the histone chaperone Asf1, which forms a complex with Rad53, is also required for Rad52 binding to replicative DNA damage. This role is independent of histone H3K56 acetylation and chromatin assembly, but also of the interactions between Asf1 with Rad53 and histones. We are currently exploring the mechanisms by which Cdc7, Rad53 and Asf1 stabilize Rad52 at replicative lesions during S phase.Peer Reviewe