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| == Function == | | == Function == |
| [https://www.uniprot.org/uniprot/POLI_HUMAN POLI_HUMAN] Error-prone DNA polymerase specifically involved in DNA repair. Plays an important role in translesion synthesis, where the normal high-fidelity DNA polymerases cannot proceed and DNA synthesis stalls. Favors Hoogsteen base-pairing in the active site. Inserts the correct base with high-fidelity opposite an adenosine template. Exhibits low fidelity and efficiency opposite a thymidine template, where it will preferentially insert guanosine. May play a role in hypermutation of immunogobulin genes. Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but may not have lyase activity.<ref>PMID:11013228</ref> <ref>PMID:11251121</ref> <ref>PMID:11387224</ref> <ref>PMID:12410315</ref> <ref>PMID:14630940</ref> <ref>PMID:15199127</ref> <ref>PMID:15254543</ref> | | [https://www.uniprot.org/uniprot/POLI_HUMAN POLI_HUMAN] Error-prone DNA polymerase specifically involved in DNA repair. Plays an important role in translesion synthesis, where the normal high-fidelity DNA polymerases cannot proceed and DNA synthesis stalls. Favors Hoogsteen base-pairing in the active site. Inserts the correct base with high-fidelity opposite an adenosine template. Exhibits low fidelity and efficiency opposite a thymidine template, where it will preferentially insert guanosine. May play a role in hypermutation of immunogobulin genes. Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but may not have lyase activity.<ref>PMID:11013228</ref> <ref>PMID:11251121</ref> <ref>PMID:11387224</ref> <ref>PMID:12410315</ref> <ref>PMID:14630940</ref> <ref>PMID:15199127</ref> <ref>PMID:15254543</ref> |
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| == Publication Abstract from PubMed ==
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| DNA polymerase (pol) iota is a Y-family polymerase involved in translesion synthesis, exhibiting higher catalytic activity with Mn2+ than Mg2+. The human germline R96G variant impairs both Mn2+- and Mg2+-dependent activities of pol iota, while the Delta1-25 variant selectively enhances its Mg2+-dependent activity. We analyzed pre-steady-state kinetic and structural effects of these two metal ions and genetic variations on pol iota using pol iota core (residues 1-445) proteins. The presence of Mn2+ (0.15 mM) instead of Mg2+ (2 mM) caused a 770-fold increase in efficiency (kpol/Kd,dCTP) of pol iota for dCTP insertion opposite G, mainly due to a 450-fold decrease in Kd,dCTP. The R96G and Delta1-25 variants displayed a 53-fold decrease and a 3-fold increase, respectively, in kpol/Kd,dCTP for dCTP insertion opposite G with Mg2+ when compared to wild-type, substantially attenuated by substitution with Mn2+. Crystal structures of pol iota ternary complexes, including the primer terminus 3'-OH and a non-hydrolyzable dCTP analog opposite G with the active-site Mg2+ or Mn2+, revealed that Mn2+ achieves more optimal octahedral coordination geometry than Mg2+, with lower values in average coordination distance geometry in the catalytic metal A-site. Crystal structures of R96G revealed the loss of three H-bonds of residues Gly-96 and Tyr-93 with an incoming dNTP, due to the lack of an arginine as well as a destabilized Tyr-93 side chain secondary to the loss of a cation-pi interaction between both side chains. These results provide a mechanistic basis for alteration in pol iota catalytic function with coordinating metals and genetic variation.
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| Kinetic and Structural Impact of Metal Ions and Genetic Variations on Human DNA Polymerase iota.,Choi JY, Patra A, Yeom M, Lee YS, Zhang Q, Egli M, Guengerich FP J Biol Chem. 2016 Aug 23. pii: jbc.M116.748285. PMID:27555320<ref>PMID:27555320</ref>
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| From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br>
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| </div>
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| ==See Also== | | ==See Also== |