4q8f
Human DNA polymerase eta extending primer immediately after a phenanthriplatin adducted G
Structural highlights
DiseasePOLH_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] FunctionPOLH_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 PubMedPlatinum drugs are a mainstay of anticancer chemotherapy. Nevertheless, tumors often display inherent or acquired resistance to platinum-based treatments, prompting the search for new compounds that do not exhibit cross-resistance with current therapies. Phenanthriplatin, cis-diamminephenanthridinechloroplatinum(II), is a potent monofunctional platinum complex that displays a spectrum of activity distinct from those of the clinically approved platinum drugs. Inhibition of RNA polymerases by phenanthriplatin lesions has been implicated in its mechanism of action. The present study evaluates the ability of phenanthriplatin lesions to inhibit DNA replication, a function disrupted by traditional platinum drugs. Phenanthriplatin lesions effectively inhibit DNA polymerases nu, zeta, and kappa and the Klenow fragment. In contrast to results obtained with DNA damaged by cisplatin, all of these polymerases were capable of inserting a base opposite a phenanthriplatin lesion, but only Pol eta, an enzyme efficient in translesion synthesis, was able to fully bypass the adduct, albeit with low efficiency. X-ray structural characterization of Pol eta complexed with site-specifically platinated DNA at both the insertion and +1 extension steps reveals that phenanthriplatin on DNA interacts with and inhibits Pol eta in a manner distinct from that of cisplatin-DNA adducts. Unlike cisplatin and oxaliplatin, the efficacies of which are influenced by Pol eta expression, phenanthriplatin is highly toxic to both Pol eta+ and Pol eta- cells. Given that increased expression of Pol eta is a known mechanism by which cells resist cisplatin treatment, phenanthriplatin may be valuable in the treatment of cancers that are, or can easily become, resistant to cisplatin. Structural and mechanistic studies of polymerase eta bypass of phenanthriplatin DNA damage.,Gregory MT, Park GY, Johnstone TC, Lee YS, Yang W, Lippard SJ Proc Natl Acad Sci U S A. 2014 Jun 24;111(25):9133-8. doi:, 10.1073/pnas.1405739111. Epub 2014 Jun 9. PMID:24927576[11] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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