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|Title||Arabidopsis thaliana AtPOLK encodes a DinB-like DNA polymerase that extends mispaired primer termini and is highly expressed in a variety of tissues.|
|Publication Type||Journal Article|
|Year of Publication||2004|
|Authors||García-Ortiz MVictoria, Ariza RR, Hoffman PD, Hays JB, Roldán-Arjona T|
|Date Published||2004 Jul|
|Alternative Splicing, Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, DNA-Directed DNA Polymerase, Gene Expression, Gene Library, Molecular Sequence Data, Phylogeny, Plants, Genetically Modified, Recombinant Fusion Proteins, Sequence Homology, Amino Acid|
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.
|Alternate Journal||Plant J.|