A EUKARYOTIC ENZYME THAT CAN DISJOIN DEAD-END COVALENT COMPLEXES BETWEEN DNA AND TYPE-I TOPOISOMERASES

Citation
Sw. Yang et al., A EUKARYOTIC ENZYME THAT CAN DISJOIN DEAD-END COVALENT COMPLEXES BETWEEN DNA AND TYPE-I TOPOISOMERASES, Proceedings of the National Academy of Sciences of the United Statesof America, 93(21), 1996, pp. 11534-11539
Citations number
31
Categorie Soggetti
Multidisciplinary Sciences
ISSN journal
00278424
Volume
93
Issue
21
Year of publication
1996
Pages
11534 - 11539
Database
ISI
SICI code
0027-8424(1996)93:21<11534:AEETCD>2.0.ZU;2-I
Abstract
The covalent joining of topoisomerases to DNA is normally a transient step in the reaction cycle of these important enzymes. However, under a variety of circumstances, the covalent complex is converted to a lon g-lived or dead-end product that can result in chromosome breakage and cell death. We have discovered and partially purified an enzyme that specifically cleaves the chemical bond that joins the active site tyro sine of topoisomerases to the 3' end of DNA. The reaction products mad e by the purified enzyme on a variety of model substrates indicate tha t the enzyme cleanly hydrolyzes the tyrosine-DNA phosphodiester linkag e, thereby liberating a DNA terminated with a 3' phosphate. The wide d istribution of this phosphodiesterase in eukaryotes and its specificit y for tyrosine linked to the 3' end but not the 5' end of DNA suggest that it plays a role in the repair of DNA trapped in complexes involvi ng eukaryotic topoisomerase I.