Cell proliferation and survival require the faithful maintenance and propagation of genetic information, which are threatened by the ubiquitous sources of DNA damage present intracellularly and in the external environment. A system of DNA repair, called the DNA damage response (DDR), detects and repairs damaged DNA and prevents cell division until the repair is complete. Here we report that methylation at the 6 position of adenosine (m6A) in RNA is rapidly (within 2 minutes) and transiently induced at DNA damage sites in response to UV. This modification occurs on numerous poly(A)+ transcripts and is regulated by the methyltransferase METTL31 and the demethylase FTO2. In the absence of METTL3 catalytic activity, cells showed delayed repair of UV-induced cyclobutane pyrimidine (CPD) adducts and elevated sensitivity to UV, demonstrating the importance of m6A in the UV-responsive DDR. Multiple DNA polymerases are involved in the UV response, some of which resynthesize DNA after the lesion has been excised by the nucleotide excision repair (NER) pathway3, while others participate in trans-lesion synthesis (TLS) to allow replication past damaged lesions in S phase4. DNA polymerase κ (Pol κ), which has been implicated in both NER and TLS5,6, required the catalytic activity of METTL3 for immediate localization to UV-induced DNA damage sites. Importantly, Pol κ over-expression qualitatively suppressed the CPD removal defect associated with METTL3 loss. Taken together, we have uncovered a novel function for RNA m6A modification in the UV-induced DDR, and our findings collectively support a model whereby m6A RNA serves as a beacon for the selective, rapid recruitment of Pol κ to damage sites to facilitate repair and cell survival.

Histone methylation is a dynamic process that participates in a diverse array of cellular processes and has been found to associate with cancer. Recently, several histone demethylases have been identified that catalyze the removal of methylation from histone H3 lysine residues. Through bioinformatic and biochemical analysis, we identified JARID1B as a H3K4 demethylase. Overexpression of JARID1B resulted in loss of tri-, di-, and monomethyl H3K4 but did not affect other histone lysine methylations. In vitro biochemical experiments demonstrated that JARID1B directly catalyzes the demethylation. The enzymatic activity requires the JmjC domain and uses Fe(II) and ␣-ketoglutarate as cofactors. Furthermore, we found that JARID1B is up-regulated in prostate cancer tissues, compared with benign prostate samples. We also demonstrated that JARID1B associates with androgen receptor and regulates its transcriptional activity. Thus, we identified JARID1B as a demethylase capable of removing three methyl groups from histone H3 lysine 4 and up-regulated in prostate cancer. Histone methylation plays an important role in regulating chromatin dynamics and transcription (1). Methylation can occur on either arginine or lysine residues (2). Each lysine can undergo three distinct stages of methylation, having either one (mono), two (di), or three (tri) methyl groups covalently bonded to the amine group of the lysine side chain, and arginine can be mono-or dimethylated (3). Depending on specific residues, methylation can either activate or repress transcription. In general, lysine methylation at H3K9, H3K27, and H4K20 is associated with transcriptional repression, whereas methylation at H3K4, H3K36, and H3K79 is associated with transcriptional activation. However, recent findings have blurred this generality. For example, methylation at H3K9 can result in transcriptional activation, and methylation at H3K36 can repress transcription (4, 5).Methylation had long been considered a stable modification, but recent studies have proved otherwise (6-16). The first histone demethylase identified is LSD1, which can remove di-and monomethylation from H3K4 by using an amine oxidase reaction (8). Subsequently, a JmjC domain-containing protein was identified to possess histone demethylase activity, and the JmjC domain was shown as a demethylase signature motif (9). This class of enzymes catalyzes the removal of methylation by using a hydroxylation reaction and required iron and ␣-ketoglutarate as cofactors. Based on this demethylase signature motif, several proteins were identified to be histone lysine demethylases (6,7,(10)(11)(12)(13)(14)(15)(16).Prostate cancer is the most common nonskin cancer and the second leading cause of cancer in America. Histone methylation has been suggested to be associated with prostate cancer. For example, it was demonstrated that histone methylations and acetylations can be used to predict the risk of prostate cancer recurrence (17). In addition, EZH2, a H3K27 methyltransferase, is shown to be involved in progression...

Lysine-specific demethylase 1 (LSD1) has been reported to repress and activate transcription by mediating histone H3K4me1/2 and H3K9me1/2 demethylation, respectively. The molecular mechanism that underlies this dual substrate specificity has remained unknown. Here we report that an isoform of LSD1, LSD1+8a, does not have the intrinsic capability to demethylate H3K4me2. Instead, LSD1+8a mediates H3K9me2 demethylation in collaboration with supervillin (SVIL), a new LSD1+8a interacting protein. LSD1+8a knockdown increases H3K9me2, but not H3K4me2, levels at its target promoters and compromises neuronal differentiation. Importantly, SVIL co-localizes to LSD1+8a-bound promoters, and its knockdown mimics the impact of LSD1+8a loss, supporting SVIL as a cofactor for LSD1+8a in neuronal cells. These findings provide insight into mechanisms by which LSD1 mediates H3K9me demethylation and highlight alternative splicing as a means by which LSD1 acquires selective substrate specificities (H3K9 versus H3K4) to differentially control specific gene expression programs in neurons.