Specificity of recA441-mediated (tif-1) mutational events. |
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Authors: | Fumio Yatagai Jennifer A. Halliday Barry W. Glickman |
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Affiliation: | (1) Department of Biology, York University, 4700 Keele Street, M3J 1P3 Toronto, Ontario, Canada;(2) Present address: Radiation Laboratory, The Institute of Physical and Chemical Research, 351-01 Wako-shi, Saitama, Japan |
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Abstract: | Summary To investigate the impact of SOS induction on the distribution of spontaneous mutation, 111 recA441-mediated mutations were characterized at the DNA sequence level in the lacI gene of Escherichia coli. A 2.6-fold enhancement in lacI– mutation frequency was observed after induction of the SOS system in the absence of mutagenic treatment, and specific classes of mutational events were induced. G : C C : G, G : C T : A and A : T T : A transversion events were specifically enhanced after SOS induction. A preferential 5-Y-Purine-3 neighbouring base specificity for these transversion events is reported here (normalised for mutation of the purine residue). In addition, a preference for transversion events at 5-C/GTGG-3 sequences is also observed. Fifty events were recovered at the lacI frameshift hotspot site and were equally represented by 4 bp addition and deletion events. This 1:1 ratio deviates significantly from the 4:1 distribution characteristic of spontaneous frameshift mutation in the RecA+ background and is a consequence of the fourfold induction of the (–)4 event. This abberrant distribution was confirmed by oligomeric probing of 474 independent recA441-mediated spontaneous lacI– mutations. |
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Keywords: | recA441 SOS-induced transversions Frameshift hotspot lacI– specificity |
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