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Structural insights into the mechanism of double strand break formation by Hermes, a hAT family eukaryotic DNA transposase

Some DNA transposons relocate from one genomic location to another using a mechanism that involves generating double-strand breaks at their transposon ends by forming hairpins on flanking DNA. The same double-strand break mode is employed by the V(D)J recombinase at signal-end/coding-end junctions d...

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Detalles Bibliográficos
Autores principales: Hickman, Alison B, Voth, Andrea Regier, Ewis, Hosam, Li, Xianghong, Craig, Nancy L, Dyda, Fred
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6212770/
https://www.ncbi.nlm.nih.gov/pubmed/30239795
http://dx.doi.org/10.1093/nar/gky838
Descripción
Sumario:Some DNA transposons relocate from one genomic location to another using a mechanism that involves generating double-strand breaks at their transposon ends by forming hairpins on flanking DNA. The same double-strand break mode is employed by the V(D)J recombinase at signal-end/coding-end junctions during the generation of antibody diversity. How flanking hairpins are formed during DNA transposition has remained elusive. Here, we describe several co-crystal structures of the Hermes transposase bound to DNA that mimics the reaction step immediately prior to hairpin formation. Our results reveal a large DNA conformational change between the initial cleavage step and subsequent hairpin formation that changes which strand is acted upon by a single active site. We observed that two factors affect the conformational change: the complement of divalent metal ions bound by the catalytically essential DDE residues, and the identity of the –2 flanking base pair. Our data also provides a mechanistic link between the efficiency of hairpin formation (an A:T basepair is favored at the –2 position) and Hermes' strong target site preference. Furthermore, we have established that the histidine residue within a conserved C/DxxH motif present in many transposase families interacts directly with the scissile phosphate, suggesting a crucial role in catalysis.