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Histone modification via rapid cleavage of C4'-oxidized abasic sites in nucleosome core particles.

ABSTRACT: The C4'-oxidized abasic site is produced in DNA by a variety of oxidizing agents, including potent cytotoxic antitumor agents. Independent generation of this alkali-labile lesion at defined positions within nucleosome core particles reveals that the histone proteins increase strand scission between 130- and 550-fold. Strand scission proceeds via a Schiff base intermediate, but the DNA-protein cross-links are unstable. The oxidized abasic site is removed in its entirety from the DNA and transferred to the lysine-rich tail region of the proximal histone protein in the form of a lactam. The modification is distributed over several residues within the amino-terminal tail of the proximal histone. Transfer of DNA damage to histones could affect gene regulation.

SUBMITTER: Zhou C

PROVIDER: S-EPMC3638250 | biostudies-literature | 2013 Apr

REPOSITORIES: biostudies-literature

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Histone modification via rapid cleavage of C4'-oxidized abasic sites in nucleosome core particles.

Zhou Chuanzheng C Sczepanski Jonathan T JT Greenberg Marc M MM

Journal of the American Chemical Society 20130326 14

The C4'-oxidized abasic site is produced in DNA by a variety of oxidizing agents, including potent cytotoxic antitumor agents. Independent generation of this alkali-labile lesion at defined positions within nucleosome core particles reveals that the histone proteins increase strand scission between 130- and 550-fold. Strand scission proceeds via a Schiff base intermediate, but the DNA-protein cross-links are unstable. The oxidized abasic site is removed in its entirety from the DNA and transferr ...[more]

PMID: 23531104

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DNA polymerase λ inactivation by oxidized abasic sites.

Project description:Base excision repair (BER) plays a vital role in maintaining genomic integrity in mammalian cells. DNA polymerase λ (Pol λ) is believed to play a backup role to DNA polymerase β (Pol β) in base excision repair. Two oxidized abasic lesions that are produced by a variety of DNA-damaging agents, including several antitumor antibiotics, the C4'-oxidized abasic site following Ape1 incision (pC4-AP), and 5'-(2-phosphoryl-1,4-dioxobutane) (DOB), irreversibly inactivate Pol β and Pol λ. The interactions of DOB and pC4-AP with Pol λ are examined in detail using DNA substrates containing these lesions at defined sites. Single-turnover kinetic experiments show that Pol λ excises DOB almost 13 times more slowly than a 5'-phosphorylated 2-deoxyribose (dRP). pC4-AP is excised approximately twice as fast as DOB. The absolute rate constants are considerably slower than those reported for Pol β for the respective reactions, suggesting that Pol λ may be an inefficient backup in BER. DOB inactivates Pol λ approximately 3-fold less efficiently than it does Pol β, and the difference can be attributed to a higher K(I) (33 ± 7 nM). Inactivation of Pol λ's lyase activity by DOB also prevents the enzyme from conducting polymerization following preincubation of the protein and DNA. Mass spectral analysis of GluC-digested Pol λ inactivated by DOB shows that Lys324 is modified. There is inferential support for the idea that Lys312 may also be modified. Both residues are within the Pol λ lyase active site. When acting on pC4-AP, Pol λ achieves approximately four turnovers on average before being inactivated. Lyase inactivation by pC4-AP is also accompanied by loss of polymerase activity, and mass spectrometry indicates that Lys312 and Lys324 are modified by the lesion. The ability of DOB and pC4-AP to inactivate Pol λ provides additional evidence that these lesions are significant sources of the cytotoxicity of DNA-damaging agents that produce them.

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