An ATM homologue from Arabidopsis thaliana: complete genomic organisation and expression analysis

ATM is a gene mutated in the human disease ataxia telangiectasia with repor ted homologues in yeast, Drosophila, Xenopus and mouse. Whenever mutants ar e available they all indicate a role of this gene family in the cellular re sponse to DNA damage. Here, we present the identification and molecular cha racterisation of the first plant homologue of ATM, The genomic locus of AtA TM (Arabidopsis thaliana homologue of ATM) spans over 30 kb and is transcri bed into a 12 kb mRNA resulting from the splicing of 79 exons, It is a sing le copy gene and maps to the long arm of chromosome 3. Transcription of Ata TM is ubiquitous and not induced by ionising radiation. The putative protei n encoded by AtATM is 3856 amino acids long and contains a phosphatidyl ino sitol-3 kinase-like (Pi3k-l) domain and a rad3 domain, features shared by o ther members of the ATM family. The AtAtm protein is highly similar to Atm, with 67 and 45% similarity in the Pi3k-l and rad3 domains respectively. In terestingly, the N-terminal portion of the protein harbours a PWWP domain, which is also present in other proteins involved in DNA metabolism such as human mismatch repair enzyme Msh6 and the mammalian de novo methyl transfer ases, Dnmt3a/b.