New DNA Repair Systems and New Insights on Old Systems in Escherichia coli

Abstract

One can deduce the extreme importance of maintaining the integrity of cellular DNA, simply by noting the numerous and diverse types of systems that a cell has at its disposal for the repair of damaged DNA (for reviews, see references 1-3). There is a repair system that requires visible light (i. e., photoreactivation), and several systems that can work in the absence of light. There are repair systems that can function in the absence of DNA replication (e. g., excision repair), and systems that can only function after damaged DNA has been replicated (i. e., postreplication repair). There are systems for the repair of DNA base damage, and systems for the repair of single-strand and double-strand breaks in DNA. Certain alterations in DNA can be repaired by more than one type of repair system, suggesting that cells have “backup ” systems for DNA repair. Some of these repair systems are constitutive and some are inducible. Finally, some of these repair systems are error-free and some are error-prone (i. e., the repair is not accurate and, therefore, produces mutations). Within the space limitations for this review, we will describe some new DNA repair systems and discuss new insights on some old repair systems in Escherichia coli.