Ultraviolet irradiation produces novel endonuclease III-sensitive cytosine photoproducts at dipyrimidine sites

J. Jen, D. L. Mitchell, R. P. Cunningham, C. A. Smith, J. S. Taylor, J. E. Cleaver

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Ultraviolet light irradiation of DNA in vitro and in vivo induces cyclobutane dimers, (6-4) pyrimidine-pyrimidone photoproducts and a variety of minor products. Using a defined DNA fragment, we have identified two classes of sites that can be cleaved by Escherichia coli endonuclease III: single cytosines whose heat lability corresponds to that of cytosine hydrates and more heat-stable dipyrimidines containing cytosine. The dipyrimidine products are induced at sites suggestive of (6-4) photoproducts but are not recognized as (6-4) photoproducts by radioimmunoassay. Use of oligonucleotides containing a single cyclobutane thymine dimer, a (6-4) photoproduct or the Dewar photoisomer of the (6-4) photoproduct also indicated that these products are not substrates for endonuclease III. We have therefore identified a minor UV photoproduct that has the same sequence specificity as the two major dipyrimidine photoproducts; it may be a minor isomer, a unique derivative or an oxidative lesion confined to dipyrimidine sites. Its biological significance is not yet known but may be masked by the preponderance of major products at the same sites. Its occurrence at the particular site in dipyrimidine sequences involved in the mutagenic action of UV photoproducts suggests that it may play a role in generating C to T transitions that are common UV-induced mutations.

Original languageEnglish (US)
Pages (from-to)323-329
Number of pages7
JournalPhotochemistry and Photobiology
Volume65
Issue number2
DOIs
StatePublished - Feb 1997

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

Fingerprint Dive into the research topics of 'Ultraviolet irradiation produces novel endonuclease III-sensitive cytosine photoproducts at dipyrimidine sites'. Together they form a unique fingerprint.

  • Cite this