A novel and unified two-metal mechanism for DNA cleavage by type II and IA topoisomerases

Article

关键词: SINGLE-STRANDED-DNA;    CRYSTAL-STRUCTURE;    ACTIVE-SITE;    RELIGATION REACTION;    PURIFICATION;    SUBSTRATE;    DOMAIN;    COMPLEXES;    CATALYSIS;    TRANSPORT;   

DOI  :  10.1038/nature08974

来源: SCIE

【 摘 要 】

Type II topoisomerases are required for the management of DNA tangles and supercoils(1), and are targets of clinical antibiotics and anticancer agents(2). These enzymes catalyse the ATP-dependent passage of one DNA duplex (the transport or T-segment) through a transient, double-stranded break in another (the gate or G-segment), navigating DNA through the protein using a set of dissociable internal interfaces, or 'gates'(3,4). For more than 20 years, it has been established that a pair of dimer-related tyrosines, together with divalent cations, catalyse G-segment cleavage(5-7). Recent efforts have proposed that strand scission relies on a 'two-metal mechanism'(8-10), a ubiquitous biochemical strategy that supports vital cellular processes ranging from DNA synthesis to RNA self-splicing(11,12). Here we present the structure of the DNA-binding and cleavage core of Saccharomyces cerevisiae topoisomerase II covalently linked to DNA through its active-site tyrosine at 2.5 angstrom resolution, revealing for the first time the organization of a cleavage-competent type II topoisomerase configuration. Unexpectedly, metal-soaking experiments indicate that cleavage is catalysed by a novel variation of the classic two-metal approach. Comparative analyses extend this scheme to explain how distantly-related type IA topoisomerases cleave single-stranded DNA, unifying the cleavage mechanisms for these two essential enzyme families. The structure also highlights a hitherto undiscovered allosteric relay that actuates a molecular 'trapdoor' to prevent subunit dissociation during cleavage. This connection illustrates how an indispensable chromosome-disentangling machine auto-regulates DNA breakage to prevent the aberrant formation of mutagenic and cytotoxic genomic lesions.

【 授权许可】

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