Sub-cellular Localization And Functional Study Of ALKBH5Dioxygenase

DNA methylation damage is one of the most cytotoxic and mutagenic lesions induced by endogenous/exogenous alkylating agents by interfering DNA replication. Alkylating agents are used clinically as anti-tumor drugs, due to their extreme cytotoxicity. The E.coli AlkB (EcAlkB) protein functions as an iron-and2-oxoglutarate-dependent enzyme capable of cleaving certain methyl adducts form DNA bases through oxidative demethylation mechanism. However, there is still far from a complete understanding of the biological significance of its mammalian homologues. Based on sequence homology within the catalytic domains of EcAlkB, eight mammalian proteins have been named EcAlkB homologues (ALKBH1-8), as well as the obesity-associated protein FTO. Amid them, these first three ALKBH1-3and FTO have been shown to remove methyl adducts form DNA similar to that of EcAlkB. Whereas ALKBH8has been recently demonstrated to work as a tRNA methyltransferase required for wobble uridine modification and DNA Damage survival, and contribute to human bladder cancer progression. But the biological functions of the rest of ALKBH proteins are still unknown. My recent experimental results suggest that ALKBH5may directly or indirectly modulate biological process by acting on RNA substrates. ALKBH5was found to possess two discrete RNase-sensitive sub-cellular locations:one into nucleoli FC and DFC, the other in nuclear speckle. Ch-IP experiment demonstrated that ALKBH5binds to rDNAs. Interestingly, ALKB5deficiency induced by RNAi leads to hyper-synthesis of nascent RNAs in cells, probably an indirect result from H3K4Me2/3demethylation. Thus ALKBH5may regulate biological process via demethylating some types of RNAs.