Abstract
DNA-binding protein HU is highly conserved in bacteria and has been implicated in a range of cellular processes and phenotypes. Like eukaryotic histones, HU is subjected to post-translational modifications. Specifically, acetylation of several lysine residues have been reported in both homologs of Escherichia coli HU. Here, we investigated the effect of acetylation at Lys67 and Lys86, located in the DNA binding-loop and interface of E. coli HUβ, respectively. Using the technique of genetic code expansion, homogeneous HUβ(K67ac) and HUβ(K86ac) protein units were obtained. Acetylation at Lys86 seemed to have negligible effects on protein secondary structure and thermal stability. Nevertheless, we found that this site-specific acetylation can regulate DNA binding by the HU homodimer but not the heterodimer. Intriguingly, while Lys86 acetylation reduced the interaction of the HU homodimer with short double-stranded DNA containing a 2-nucleotide gap or nick, it enhanced the interaction with longer DNA fragments and had minimal effect on a short, fully complementary DNA fragment. These results demonstrate the complexity of post-translational modifications in functional regulation, as well as indicating the role of lysine acetylation in tuning bacterial gene transcription and epigenetic regulation.
Highlights
Histone-like protein HU is a prevalent DNA-binding protein ubiquitous among bacterial species (Grove, 2011)
The results demonstrate the complexity of bacterial post-translational modification in functional regulation, as well as indicating that lysine acetylation may fine tune gene transcription in bacteria and be involved in epigenetic regulation
Post-translational modification of Lys86 was implicated in particular cell phenotypes, while K86R mutation led to about fourfold reduction in the number of colonies formed in the presence of an antibiotic
Summary
Histone-like protein HU is a prevalent DNA-binding protein ubiquitous among bacterial species (Grove, 2011). This basic protein is highly conserved, consisting of an α-helical “body” and two β-sheets that are extended to β-ribbon “arms” interacting directly with DNA (Swinger et al, 2003). HU can modulate the pathogenicity of different bacteria through transcriptional regulation (Alberti-Segui et al, 2010; Koli et al, 2011; Mangan et al, 2011; Wang et al, 2014; Phan et al, 2015). The majority of bacterial species produce one HU homolog, which forms homodimers (Grove, 2011).
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