5dqi
From Proteopedia
Crystal Structure of Human DNA Polymerase Eta Extending an O4-Ethylthymidine : dA Pair By Inserting dCTP Opposite dG
Structural highlights
Disease[POLH_HUMAN] Defects in POLH are the cause of xeroderma pigmentosum variant type (XPV) [MIM:278750]; also designated as XP-V. Xeroderma pigmentosum (XP) is an autosomal recessive disease due to deficient nucleotide excision repair. It is characterized by hypersensitivity of the skin to sunlight, followed by high incidence of skin cancer and frequent neurologic abnormalities. XPV shows normal nucleotide excision repair, but an exaggerated delay in recovery of replicative DNA synthesis. Most XPV patients do not develop clinical symptoms and skin neoplasias until a later age. Clinical manifestations are limited to photo-induced deterioration of the skin and eyes.[1] [2] [3] [4] [5] Function[POLH_HUMAN] 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. Plays an important role in the repair of UV-induced pyrimidine dimers. Depending on the context, it inserts the correct base, but causes frequent base transitions and transversions. May play a role in hypermutation at immunoglobulin genes. Forms a Schiff base with 5'-deoxyribose phosphate at abasic sites, but does not have lyase activity. Targets POLI to replication foci.[6] [7] [8] [9] [10] Publication Abstract from PubMedDNA lesions that elude repair may undergo translesion synthesis catalyzed by Y-family DNA polymerases. O(4)-Alkylthymidines, persistent adducts that can result from carcinogenic agents, may be encountered by DNA polymerases. The influence of lesion orientation around the C4-O(4) bond on processing by human DNA polymerase eta (hPol eta) was studied for oligonucleotides containing O(4)-methylthymidine, O(4)-ethylthymidine, and analogs restricting the O(4)-methylene group in an anti-orientation. Primer extension assays revealed that the O(4)-alkyl orientation influences hPol eta bypass. Crystal structures of hPol eta*DNA*dNTP ternary complexes with O(4)-methyl- or O(4)-ethylthymidine in the template strand showed the nucleobase of the former lodged near the ceiling of the active site, with the syn-O(4)-methyl group engaged in extensive hydrophobic interactions. This unique arrangement for O(4)-methylthymidine with hPol eta, inaccessible for the other analogs due to steric/conformational restriction, is consistent with differences observed for nucleotide incorporation and supports the concept that lesion conformation influences extension across DNA damage. Together, these results provide mechanistic insights on the mutagenicity of O(4)MedT and O(4)EtdT when acted upon by hPol eta. Lesion Orientation of O(4)-Alkylthymidine Influences Replication by Human DNA Polymerase eta.,O'Flaherty DK, Patra A, Su Y, Guengerich FP, Egli M, Wilds CJ Chem Sci. 2016 Aug 1;7(8):4896-4904. doi: 10.1039/C6SC00666C. Epub 2016 Apr 26. PMID:27574558[11] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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