Methods in Molecular Biology • 16 Enzymes of Molecular Biology

CHAPTER 10

DNA and RNA Ligases

(EC 6.5.1.1, EC 6.5.1.2, and EC 6.5.1.3)

Martin J. Maunders

1. Introduction
   Ligases are a class of enzymes that catalyze the joining of nucleic
   acid molecules by the formation of phosphodiester bonds between
   their termini (1). The nucleic acid substrate to be linked may be DNA
   or RNA depending on the type of ligase involved.
   The enzymes are widespread and have been identified in a range of
   organisms, including bacteria (2, 3), phage-infected bacteria (4), yeasts
   (5), amphibians (6), and mammals (5), including Homo sapiens (7).
   Many ligase-deficient and ligase-overproducing mutants have been
   isolated, and levels of enzyme in the E. coli bacterium can vary 1000-
   fold (from 0.01 to 10 x normal) without deleterious effect.


2. DNA Ligases (EC 6.5.1.1-2)
   The role of DNA ligases in vivo is believed to include the joining
   of short DNA fragments formed during DNA replication (8), and so
   enabling DNA synthesis to progress in an overall 3'-5' direction on the
   antiparallel strand of the double helix, while continual 5'-3' synthesis
   proceeds on the other strand.
   Other possible functions of DNA ligases include roles during genetic
   recombination and in the repair of UV-damaged DNA (9), though
   ligase- bacterial mutants can in general perform these functions suf-
   ficiently well. In yeast, however, there is evidence to support the idea
   of a role for DNA ligases in UV damage repair (10).

From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology

Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

213