Protein Flexibility and Synergy of HMG Domains Underlie U-Turn Bending of DNA by TFAM in Solution

TitleProtein Flexibility and Synergy of HMG Domains Underlie U-Turn Bending of DNA by TFAM in Solution
Publication TypeJournal Article
Year of Publication2018
AuthorsRubio-Cosials, Anna, Battistini Federica, Gansen Alexander, Cuppari Anna, Bernadó Pau, Orozco Modesto, Langowski Jörg, Tóth Katalin, and Solà Maria
JournalBiophysical Journal
Volume114
Pagination2386 - 2396
Date Published05/2018
ISSN0006-3495
Abstract

Human mitochondrial transcription factor A (TFAM) distorts DNA into a U-turn, as shown by crystallographic studies. The relevance of this U-turn is associated with transcription initiation at the mitochondrial light strand promoter (LSP). However, it has not been yet discerned whether a tight U-turn or an alternative conformation, such as a V-shape, is formed in solution. Here, single-molecule FRET experiments on freely diffusing TFAM/LSP complexes containing different DNA lengths show that a DNA U-turn is induced by progressive and cooperative binding of the two TFAM HMG-box domains and the linker between them. SAXS studies further show compaction of the protein upon complex formation. Finally, molecular dynamics simulations reveal that TFAM/LSP complexes are dynamic entities, and the HMG boxes induce the U-turn against the tendency of the DNA to adopt a straighter conformation. This tension is resolved by reversible unfolding of the linker, which is a singular mechanism that allows a flexible protein to stabilize a tight bending of DNA.

URLhttp://www.sciencedirect.com/science/article/pii/S0006349517349755
DOI10.1016/j.bpj.2017.11.3743
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