Ordered intracellular RecA–DNA assemblies: A potential site of in vivo RecA-mediated activities

^*Department of Organic Chemistry, and ^†Electron Microscopy Center, Weizmann Institute of Science, Rehovot 76100, Israel

Edited by Charles M. Radding, Yale University School of Medicine, New Haven, CT, and approved March 9, 2000 (received for review December 8, 1999)

Abstract

The inducible SOS response increases the ability of bacteria to cope with DNA damage through various DNA repair processes in which the RecA protein plays a central role. Here we present the first study of the morphological aspects that accompany the SOS response in Escherichia coli. We find that induction of the SOS system in wild-type bacteria results in a fast and massive intracellular coaggregation of RecA and DNA into a lateral macroscopic assembly. The coaggregates comprise substantial portions of both the cellular RecA and the DNA complement. The structural features of the coaggregates and their relation to in vitro RecA–DNA networks, as well as morphological studies of strains carrying RecA mutants, are all consistent with the possibility that the intracellular assemblies represent a functional entity in which RecA-mediated DNA repair and protection activities occur.

Footnotes

↵ ‡ To whom reprint requests should be addressed. E-mail: avi.minsky{at}weizmann.ac.il.
This paper was submitted directly (Track II) to the PNAS office.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.090532397.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.090532397
Abbreviations:

dsDNA,

double-stranded DNA