Mutations are permanent DNA sequence changes that can be induced when replication occurs on a damaged DNA template. In Escherichia coli, the process of translesion synthesis pasta lesion that hinders replication requires the induction of SOS-controlled gene products, among which are those of the umuDC operon. To study translesion synthesis in vivo, we have constructed single-stranded vectors containing single 2-acetylaminofluorene adducts located within -1 and -2 frameshift mutation hot spots formed by short repetitive sequences. These adducts strongly hinder DNA replication as only 2-5% of the molecules give rise to progeny under non-SOS-induced conditions. Induction of the SOS response lead to a 10-fold increase in survival. Adducts present within repetitive sequences trigger the formation of misaligned primer/template replication intermediates which, upon elongation, will result in the fixation of frameshift errors (mutagenic translesion synthesis). Surprisingly we find that elongation from the nonslipped intermediate depends upon functional umuDC+ gene products, whereas elongation from the slipped intermediate is umuDC+ independent but requires another, as yet biochemically uncharacterized, SOS function. These data are discussed in terms of the different steps involved during translesion synthesis through a replication-blocking lesion.

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Proceedings of the National Academy of Sciences of the United States of America
Department of Biology

Napolitano, R.L. (Rita L.), Lambert, I, & Fuchs, R.P.P. (Robert P. P.). (1997). SOS factors involved in translesion synthesis. Proceedings of the National Academy of Sciences of the United States of America, 94(11), 5733–5738. doi:10.1073/pnas.94.11.5733