A Sir2 family protein Rv1151c deacetylates HU to alter its DNA binding mode in Mycobacterium tuberculosis

Abstract

Till recently, knowledge about epigenetic regulation in bacterial world confined largely to DNA methylation. Lysine acetylation/deacetylation of histones is a major contributor for chromatin dynamics in eukaryotes. However, little is known about such epigenetic changes brought about by post-translational modifications in bacteria. Here, we describe an example of such mechanism occurring in a histone like protein, HU from Mycobacterium tuberculosis (Mtb). Previously, we demonstrated the interaction and acetylation of Mtb HU (MtHU) by one of the acetyl transferases, Eis. In this work, we demonstrate the deacetylation of acetylated HU (MtHU^Ac) by Rv1151c, the only Sir2 like protein discovered in Mtb. The DNA binding properties of MtHU are significantly altered upon acetylation but reversed consequent to deacetylation by the deacetylase. Deacetylated HU (MtHU^dAc) bound to relaxed DNA leading to the formation of looped and dense molecules as compared to open structures formed by its acetylated form. Interaction of MtHU^dAc with linear DNA modifies its organization leading to formation of highly bridged compact structures while binding of MtHU^Ac leads to the formation of stiff and straight rods. That a nucleoid associated protein can undergo acetylation/deacetylation to alter its DNA binding and architectural role opens up a new dimension of investigation of epigenetic regulation in mycobacteria.

Keywords: Acetylation; Deacetylation; HU; Nucleoid associated proteins; Rv1151c; Sirtuin.