Structure and expression of AtPMS1, the arabidopsis ortholog of the yeast DNA repair gene PMS1

The DNA mismatch repair (MMR) machinery of eukaryotes involves several genes whose products interact to repair mispaired bases resulting from DNA replication errors or homoeologous recombination. We report here the cloning and characterization of AtPMS1, a gene that codes for a predicted polypeptide sequence of 924 amino acids containing the typical MutL motifs. It is one of three homologs of the Escherichia coli MutL gene in Arabidopsis thaliana and constitutes the first ortholog of the yeast PMS1 gene to be characterized in plants. The gene is present in a single copy in the Arabidopsis genome and is located in the top portion of chromosome IV. Northern and RT-PCR analyses indicate that the AtPMS1 gene is expressed at very low levels in mature leaves but is much more highly expressed in cultured cells. Furthermore, an alternate form of the messenger, apparently coding for an incomplete protein lacking a key portion of the C-terminus, appears to co-exist in some plant tissues, albeit at a lower abundance. Primer extension and 5'-RACE experiments suggest that this gene has multiple transcription start sites. observations that are in agreement with the lack of a detectable TATA box. These results underline the importance of experimentally-derived results to confirm and, occasionally, to correct and extend the information provided by genome projects. (C) 2004 Elsevier Ireland Ltd. All rights reserved.