Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.

RecQ helicases are essential for the maintenance of chromosome stability. In addition to DNA unwinding, some RecQ enzymes have an intrinsic DNA strand annealing activity. The function of this dual enzymatic activity and the mechanism that regulates it is, however, unknown. Here, we describe two quat...

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Main Authors: Laura Muzzolini, Fabienne Beuron, Ardan Patwardhan, Venkateswarlu Popuri, Sheng Cui, Benedetta Niccolini, Mathieu Rappas, Paul S Freemont, Alessandro Vindigni
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2007-02-01
Series:PLoS Biology
Online Access:https://doi.org/10.1371/journal.pbio.0050020
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spelling doaj-f6fc8feed45645e59e75881fe6900f442021-07-02T16:25:50ZengPublic Library of Science (PLoS)PLoS Biology1544-91731545-78852007-02-0152e2010.1371/journal.pbio.0050020Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.Laura MuzzoliniFabienne BeuronArdan PatwardhanVenkateswarlu PopuriSheng CuiBenedetta NiccoliniMathieu RappasPaul S FreemontAlessandro VindigniRecQ helicases are essential for the maintenance of chromosome stability. In addition to DNA unwinding, some RecQ enzymes have an intrinsic DNA strand annealing activity. The function of this dual enzymatic activity and the mechanism that regulates it is, however, unknown. Here, we describe two quaternary forms of the human RECQ1 helicase, higher-order oligomers consistent with pentamers or hexamers, and smaller oligomers consistent with monomers or dimers. Size exclusion chromatography and transmission electron microscopy show that the equilibrium between the two assembly states is affected by single-stranded DNA (ssDNA) and ATP binding, where ATP or ATPgammaS favors the smaller oligomeric form. Our three-dimensional electron microscopy reconstructions of human RECQ1 reveal a complex cage-like structure of approximately 120 A x 130 A with a central pore. This oligomeric structure is stabilized under conditions in which RECQ1 is proficient in strand annealing. In contrast, competition experiments with the ATPase-deficient K119R and E220Q mutants indicate that RECQ1 monomers, or tight binding dimers, are required for DNA unwinding. Collectively, our findings suggest that higher-order oligomers are associated with DNA strand annealing, and lower-order oligomers with DNA unwinding.https://doi.org/10.1371/journal.pbio.0050020
collection DOAJ
language English
format Article
sources DOAJ
author Laura Muzzolini
Fabienne Beuron
Ardan Patwardhan
Venkateswarlu Popuri
Sheng Cui
Benedetta Niccolini
Mathieu Rappas
Paul S Freemont
Alessandro Vindigni
spellingShingle Laura Muzzolini
Fabienne Beuron
Ardan Patwardhan
Venkateswarlu Popuri
Sheng Cui
Benedetta Niccolini
Mathieu Rappas
Paul S Freemont
Alessandro Vindigni
Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.
PLoS Biology
author_facet Laura Muzzolini
Fabienne Beuron
Ardan Patwardhan
Venkateswarlu Popuri
Sheng Cui
Benedetta Niccolini
Mathieu Rappas
Paul S Freemont
Alessandro Vindigni
author_sort Laura Muzzolini
title Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.
title_short Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.
title_full Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.
title_fullStr Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.
title_full_unstemmed Different quaternary structures of human RECQ1 are associated with its dual enzymatic activity.
title_sort different quaternary structures of human recq1 are associated with its dual enzymatic activity.
publisher Public Library of Science (PLoS)
series PLoS Biology
issn 1544-9173
1545-7885
publishDate 2007-02-01
description RecQ helicases are essential for the maintenance of chromosome stability. In addition to DNA unwinding, some RecQ enzymes have an intrinsic DNA strand annealing activity. The function of this dual enzymatic activity and the mechanism that regulates it is, however, unknown. Here, we describe two quaternary forms of the human RECQ1 helicase, higher-order oligomers consistent with pentamers or hexamers, and smaller oligomers consistent with monomers or dimers. Size exclusion chromatography and transmission electron microscopy show that the equilibrium between the two assembly states is affected by single-stranded DNA (ssDNA) and ATP binding, where ATP or ATPgammaS favors the smaller oligomeric form. Our three-dimensional electron microscopy reconstructions of human RECQ1 reveal a complex cage-like structure of approximately 120 A x 130 A with a central pore. This oligomeric structure is stabilized under conditions in which RECQ1 is proficient in strand annealing. In contrast, competition experiments with the ATPase-deficient K119R and E220Q mutants indicate that RECQ1 monomers, or tight binding dimers, are required for DNA unwinding. Collectively, our findings suggest that higher-order oligomers are associated with DNA strand annealing, and lower-order oligomers with DNA unwinding.
url https://doi.org/10.1371/journal.pbio.0050020
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