Faculty Publications

Evidence For A Bind-Then-Bend Mechanism For Architectural DNA Binding Protein Ynhp6A

Document Type

Article

Journal/Book/Conference Title

Nucleic Acids Research

Volume

47

Issue

6

First Page

2871

Last Page

2883

Abstract

The yeast Nhp6A protein (yNhp6A) is a member of the eukaryotic HMGB family of chromatin factors that enhance apparent DNA flexibility. yNhp6A binds DNA nonspecifically withnMaffinity, sharply bending DNA by >60°. It is not known whether the protein binds to unbent DNA and then deforms it, or if bent DNA conformations are 'captured' by protein binding. The former mechanism would be supported by discovery of conditions where unbent DNA is bound by yNhp6A. Here, we employed an array of conformational probes (FRET, fluorescence anisotropy, and circular dichroism) to reveal solution conditions in which an 18- base-pair DNA oligomer indeed remains bound to yNhp6A while unbent. In 100 mM NaCl, yNhp6Abound DNA unbends as the temperature is raised, with no significant dissociation of the complex detected up to ∼45°C. In 200 mM NaCl, DNA unbending in the intact yNhp6A complex is again detected up to ∼35°C. Microseconds-resolved laser temperature jump perturbation of the yNhp6a-DNA complex revealed relaxation kinetics that yielded unimolecular DNA bending/unbending rates on timescales of 500 μs-1 ms. These data provide the first direct observation of bending/unbending dynamics of DNA in complex with yNhp6A, suggesting a bind-then-bend mechanism for this protein.

Department

Department of Chemistry and Biochemistry

Original Publication Date

4-8-2019

DOI of published version

10.1093/nar/gkz022

Repository

UNI ScholarWorks, Rod Library, University of Northern Iowa

Language

en

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