Post-translational modification of nucleoid-associated proteins: an extra layer of functional modulation in bacteria?

Post-translational modification (PTM) of histones has been investigated in eukaryotes for years, revealing its widespread occurrence and functional importance. Many PTMs affect chromatin folding and gene activity. Only recently the occurrence of such modifications has been recognized in bacteria. However, it is unclear whether PTM of the bacterial counterparts of eukaryotic histones, nucleoid-associated proteins (NAPs), bears a comparable significance. Here, we scrutinize proteome mass spectrometry data for PTMs of the four most abundantly present NAPs in Escherichia coli (H-NS, HU, IHF and FIS). This approach allowed us to identify a total of 101 unique PTMs in the 11 independent proteomic studies covered in this review. Combined with structural and genetic information on these proteins, we describe potential effects of these modifications (perturbed DNA-binding, structural integrity or interaction with other proteins) on their function.