MUTAGENIC PROPERTIES OF THE T-C CYCLOBUTANE DIMER

Citation
Mj. Horsfall et al., MUTAGENIC PROPERTIES OF THE T-C CYCLOBUTANE DIMER, Journal of bacteriology, 179(9), 1997, pp. 2835-2839
Citations number
28
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ISSN journal
0021-9193
Volume
179
Issue
9
Year of publication
1997
Pages
2835 - 2839
Database
ISI
SICI code
0021-9193(1997)179:9<2835:MPOTTC>2.0.ZU;2-J
Abstract
G.C-->A.T transitions within T-C or C-C bipyrimidine sequences are by far the most frequent class of mutation induced by 254-nm UV irradiati on in most genes and species investigated, but the reason for the high degree of mutability and specificity at these sites is uncertain, Som e data implicate the deamination of cytosine to uracil as a possible c ause, but other results appear to indicate that the rate of deaminatio n is too low for this to be significant in Escherichia coli, If deamin ation is not the cause, the high degree of mutability must presumably reflect the inherent properties of T-C and C-C dimers, We investigated this question by transfecting excision-deficient and excision-profici ent strains of E, coli with single-stranded vectors that carried a sit e-specific cis-syn T-C cyclobutane dimer and by analyzing the nucleoti de sequences of replicated vector products, We found that replication past the T-C dimer, like replication past its T-T and U-U counterparts , is in fact >95% accurate and that the frequencies of bypass are also very similar for these photoproducts. Since the T-C dimer appears to be only weakly mutagenic, the high frequency of UV-induced mutations a t T-C sites presumably depends on some other process, such as deaminat ion, although the mechanism remains to be established.