%0 Journal Article %J Plant J %D 2004 %T Arabidopsis thaliana AtPOLK encodes a DinB-like DNA polymerase that extends mispaired primer termini and is highly expressed in a variety of tissues. %A García-Ortiz, Maria Victoria %A Ariza, Rafael R %A Peter D Hoffman %A John B Hays %A Roldán-Arjona, Teresa %K Alternative Splicing %K Amino Acid Sequence %K Arabidopsis %K Arabidopsis Proteins %K DNA-Directed DNA Polymerase %K Gene Expression %K Gene Library %K Molecular Sequence Data %K Phylogeny %K Plants, Genetically Modified %K Recombinant Fusion Proteins %K Sequence Homology, Amino Acid %X

Cell survival after DNA damage depends on specialized DNA polymerases able to perform DNA synthesis on imperfect templates. Most of these enzymes belong to the recently discovered Y-family of DNA polymerases, none of which has been previously described in plants. We report here the isolation, functional characterization and expression analysis of a plant representative of the Y-family. This polymerase, which we have termed AtPolkappa, is a homolog of Escherichia coli pol IV and human pol kappa, and thus belongs to the DinB subfamily. We purified AtPolkappa and found a template-directed DNA polymerase, endowed with limited processivity that is able to extend primer-terminal mispairs. The activity and processivity of AtPolkappa are enhanced markedly upon deletion of 193 amino acids (aa) from its carboxy (C)-terminal domain. Loss of this region also affects the nucleotide selectivity of the enzyme, leading to the incorporation of both dCTP and dTTP opposite A in the template. We detected three cDNA forms, which result from the alternative splicing of AtPOLK mRNA and have distinct patterns of expression in different plant organs. Histochemical localization of beta-glucuronidase (GUS) activity in transgenic plants revealed that the AtPOLK promoter is active in endoreduplicating cells, suggesting a possible role during consecutive DNA replication cycles in the absence of mitosis.

%B Plant J %V 39 %P 84-97 %8 2004 Jul %G eng %N 1 %R 10.1111/j.1365-313X.2004.02112.x