Stress Activated Protein Kinase Pathway Modulates Homologous Recombination in Fission Yeast Angela Bellini1,2, Pierre-Marie Girard1,2, Sarah Lambert1,2, Ludovic Tessier1,2, Evelyne Sage1,2, Stefania Francesconi1,2* 1 Institut Curie, Centre de Recherche, Orsay, France, 2 CNRS UMR 3348, Centre Universitaire, Orsay, France Abstract Rad52 is a key player in homologous recombination (HR), a DNA repair pathway that is dedicated to double strand breaks repair and recovery of perturbed replication forks. Here we show that fission yeast Rad52 homologue is phosphorylated when S phase cells are exposed to ROS inducers such as ultraviolet A radiation or hydrogen peroxide, but not to ultraviolet C or camptothecin. Phosphorylation does not depend on kinases Chk1, Rad3, Tel1 or Cdc2, but depends on a functional stress activated protein kinase (SAPK) pathway and can be partially prevented by anti-oxidant treatment. Indeed, cells lacking Sty1, the major fission yeast MAP kinase of the SAPK pathway, do not display Rad52 phosphorylation and have UVA induced Rad52 foci that persist longer if compared to wild type cells. In addition, spontaneous intrachromosomal HR is diminished in cells lacking Sty1 and, more precisely, gene conversion is affected. Moreover, HR induced by site-specific arrest of replication forks is twice less efficient in cells that do not express Sty1. Importantly, impairing HR by deletion of the gene encoding the recombinase Rhp51 leads to Sty1 dependent Rad52 phosphorylation. Thus, SAPK pathway impinges on early step of HR through phosphorylation of Rad52 in cells challenged by oxidative stress or lacking Rhp51 and is required to promote spontaneous gene conversion and recovery from blocked replication forks. Citation: Bellini A, Girard P-M, Lambert S, Tessier L, Sage E, et al. (2012) Stress Activated Protein Kinase Pathway Modulates Homologous Recombination in Fission Yeast. PLoS ONE 7(10): e47987. doi:10.1371/journal.pone.0047987 Editor: Marco Muzi-Falconi, Universita’ di Milano, Italy Received June 13, 2012; Accepted September 19, 2012; Published October 31, 2012 Copyright: 2012 Bellini et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by ‘‘Centre National de la Recherche Scientifique’’ and Curie Institute. A. Bellini was supported by PhD fellowships from Curie Institute and ‘‘Association pour la Recherche sur le Cancer’’. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: stefania.francesconi@curie.fr Introduction UVA radiation is the most abundant solar UV radiation that reaches earth’s surface. UVA is able to penetrate human skin deeper than UVB and reaches the basal layer of skin where actively replicating keratinocytes are present. Different from UVB, UVA is weakly absorbed by DNA and mainly acts through interaction with endogenous photosensitizers resulting in genera- tion of reactive oxygen species (ROS), predominantly singlet oxygen, which can damage all cellular components [1,2,3]. UVA induced ROS have been linked to skin photoaging [4] and increasing evidence suggest contribution to skin carcinogenesis [5]. More generally, ROS-induced cellular damage is linked to pathological conditions such as cancer, diabetes, atherosclerosis, neurodegenerative diseases and premature aging [6,7,8,9,10]. Because UVA induced biological effects are oxygen dependent, UVA is an inducer of oxidative stress and thus, cellular response to this radiation is complex. As many stresses, UVA-induced oxidative stress activates the SAPK pathways that are character- ized by a cascade of kinases highly conserved: MAPK (mitogen activated protein kinase) kinase kinases (MAPKKK), MAPK kinases (MAPKK) and MAPKs. Eventually, activation of SAPK pathways results in protection of cells from injuries through appropriate regulation of gene expression and protein translation [11,12]. In human keratinocytes the p38 MAP kinase and JNK (c- Jun N-terminal kinase) pathways are activated by UVA radiation [13]. In Schizosaccharomyces pombe (S. pombe), Sty1/Spc1 is the principal MAPK, mainly related to human p38, which is activated by phosphorylation following a variety of stresses including high osmolarity, oxidative stress, UVC exposure [14,15] and metabolic inputs such as calorie restriction and histidine starvation, two situations generating endogenous oxidative stress [16,17]. Sty1 is also required for sexual differentiation by regulating Ste11 expression, the major transcription factor required to induce meiotic genes [18]. Activation of Sty1 results in its nuclear localization and induction of gene expression mainly through the Atf1 transcription factor. Such modulation of the gene expression program will provide cells with the necessary to face stress [19]. Furthermore, Sty1, but not its major target Atf1, controls mitotic entry upon nutritional stress [20,21]. However, different degrees of Sty1 activation impact on mitotic commitment in opposite ways: basal level of Sty1 activity promotes mitotic onset while high level of Sty1 activity delays mitotic entry [22]. This function is also conserved in mammals where the extracellular signal-related kinase (ERK) is required for mitotic entry and p38 activation by stress is required for mitotic delay [23,24,25]. In addition, different ways of Sty1 activation according to the stimulus applied have been reported, implying that Sty1, similarly to mammalian SAPKs, is finely tuned in the cell [26,27,28]. Nowadays, it is well established that UVA solar radiation is a biological relevant genotoxic agent [29]. At the DNA level UVA induces formation of oxidized bases, mainly 8-oxoguanine (8- PLOS ONE | www.plosone.org 1 October 2012 | Volume 7 | Issue 10 | e47987