GSE175465
Multiple physiological roles of both specific and non-specific DNA binding modes of HU protein in Escherichia coli
The histone-like protein HU is crucial for genome organization and the expression of many genes in Escherichia coli. HU binds DNA independent of any specific nucleotide sequence but exhibits two binding affinities; low-affinity to any B-DNA (non-specific) and high affinity to DNA with distortions like kinks and cruciforms (structure-specific). We validated and defined the three conserved lysine residues, K3, K18, and K83, in HU as critical amino acid residues for the non-specific binding and the conserved P63 together with the lysine residues critical for the structure-specific binding both in vitro and in vivo. By determining the effects of disrupting the two DNA binding modes on various HU-dependent physiological processes, we demonstrate that the DNA structure-specific binding regulates expression of many genes including those involved in DNA metabolic processes that control chromosome maintenance and partition. On the other hand, HU associates with the chromosome at numerous sites primarily through the lysines-mediated non-specific binding and control chromosome dynamics and structural maintenance. Thus, we demonstrate that two different DNA binding mode of HU plays separate roles: (i) The high-affinity DNA structure-specific binding regulates many distinct DNA metabolic processes, primarily through transcription regulation. (ii) Its low-affinity, non-specific binding directly helps general organization of the genome. Overall design: Three biological replicates were analyzed for each strain