Protein Flexibility and Synergy of HMG Domains Underlie U-Turn Bending of DNA by TFAM in Solution
|Title||Protein Flexibility and Synergy of HMG Domains Underlie U-Turn Bending of DNA by TFAM in Solution|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Rubio-Cosials, Anna, Battistini Federica, Gansen Alexander, Cuppari Anna, Bernadó Pau, Orozco Modesto, Langowski Jörg, Tóth Katalin, and Solà Maria|
|Pagination||2386 - 2396|
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.