Details

Autor(en) / Beteiligte

• Schaaper, Roel M.
• Dunn, Ronnie L.

Titel

Spectra of Spontaneous Mutations in Escherichia coli Strains Defective in Mismatch Correction: The Nature of in vivo DNA Replication Errors

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 1987-09, Vol.84 (17), p.6220-6224

Ort / Verlag

Washington, DC: National Academy of Sciences of the United States of America

Erscheinungsjahr

1987

Quelle

Electronic Journals Library

Beschreibungen/Notizen

• We have determined the DNA sequence changes in 487 spontaneous mutations in the N-terminal part of the lacI gene in mutH, mutL, and mutS strains of Escherichia coli. These strains display elevated spontaneous mutation rates because of a deficiency in the process of postreplicative mismatch correction. As a consequence the mutational spectra reveal the nature of spontaneous DNA replication errors. The spectra consist of base substitutions (75%) and single-base deletions (25%). Among the base substitutions, transitions (both A· T→ G· C and G· C→ A· T) are strongly favored over transversions (96% versus 4%). Large site-to-site differences are observed among identical base substitutions, presumably reflecting the modulating effects of neighboring bases. The single-base-deletion spectrum is dominated by a large hotspot at a run of adjacent identical base pairs, implying a Streisingerslippage mechanism. The data, when compared to a previously determined wild-type spectrum, also provide information on the specificity of the mismatch repair system.