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J Biol Chem. 2003 Dec 26;278(52):52546-50. Epub 2003 Oct 22.

Escherichia coli DNA polymerase V subunit exchange: a post-SOS mechanism to curtail error-prone DNA synthesis.

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Department of Biological Sciences and Chemistry, Hedco Molecular Biology Laboratories, University of Southern California, Los Angeles, California 90089-1340, USA.


DNA polymerase V consisting of a heterotrimer composed of one molecule of UmuC and two molecules of UmuD' (UmuD'2C) is responsible for SOS damage-induced mutagenesis in Escherichia coli. Here we show that although the UmuD'2C complex remains intact through multiple chromatographic steps, excess UmuD, the precursor to UmuD', displaces UmuD' from UmuD'2C by forming a UmuDD' heterodimer, while UmuC concomitantly aggregates as an insoluble precipitate. Although soluble UmuD'2C is readily detected when the two genes are co-transcribed and translated in vitro, soluble UmuD2C or UmuDD'C are not detected. The subunit exchange between UmuD'2C and UmuD offers a biological means to inactivate error-prone polymerase V following translesion synthesis, thus preventing mutations from occurring on undamaged DNA.

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