@article {484,
	title = {Genomic analysis reveals epistatic silencing of "expensive" genes in Escherichia coli K-12. [Next Generation Genomics facility]},
	journal = {Mol Biosyst},
	volume = {9},
	year = {2013},
	month = {2013 Aug},
	pages = {2021-33},
	abstract = {<p>A barrier for horizontal gene transfer is high gene expression, which is metabolically expensive. Silencing of horizontally-acquired genes in the bacterium Escherichia coli is caused by the global transcriptional repressor H-NS. The activity of H-NS is enhanced or diminished by other proteins including its homologue StpA, and Hha and YdgT. The interconnections of H-NS with these regulators and their role in silencing gene expression in E. coli are not well understood on a genomic scale. In this study, we use transcriptome sequencing to show that there is a bi-layered gene silencing system - involving the homologous H-NS and StpA - operating on horizontally-acquired genes among others. We show that H-NS-repressed genes belong to two types, termed "epistatic" and "unilateral". In the absence of H-NS, the expression of "epistatically controlled genes" is repressed by StpA, whereas that of "unilaterally controlled genes" is not. Epistatic genes show a higher tendency to be non-essential and recently acquired, when compared to unilateral genes. Epistatic genes reach much higher expression levels than unilateral genes in the absence of the silencing system. Finally, epistatic genes contain more high affinity H-NS binding motifs than unilateral genes. Therefore, both the DNA binding sites of H-NS as well as the function of StpA as a backup system might be selected for silencing highly transcribable genes.</p>
},
	keywords = {Binding Sites, DNA-Binding Proteins, Epistasis, Genetic, Escherichia coli K12, Escherichia coli Proteins, Fimbriae Proteins, Gene Expression Regulation, Bacterial, Gene Silencing, Gene Transfer, Horizontal, Genome, Bacterial, Molecular Chaperones, Protein Binding, Repressor Proteins, Sequence Analysis, DNA, Transcription, Genetic, Transcriptome},
	issn = {1742-2051},
	doi = {10.1039/c3mb70035f},
	author = {Srinivasan, Rajalakshmi and Chandraprakash, Deepti and Krishnamurthi, Revathy and Singh, Parul and Scolari, Vittore F and Krishna, Sandeep and Seshasayee, Aswin Sai Narain}
}
@article {519,
	title = {Unexpected histone H3 tail-clipping activity of glutamate dehydrogenase. (Mass spectrometry - Proteomics)},
	journal = {J Biol Chem},
	volume = {288},
	year = {2013},
	month = {2013 Jun 28},
	pages = {18743-57},
	abstract = {<p>Clipping of histone tails has been reported in several organisms. However, the significance and regulation of histone tail clipping largely remains unclear. According to recent discoveries H3 clipping has been found to be involved in regulation of gene expression and chromatin dynamics. Earlier we had provided evidence of tissue-specific proteolytic processing of histone H3 in White Leghorn chicken liver nuclei. In this study we identify a novel activity of glutamate dehydrogenase (GDH) as a histone H3-specific protease in chicken liver tissue. This protease activity is regulated by divalent ions and thiol-disulfide conversion in vitro. GDH specifically clips H3 in its free as well as chromatin-bound form. Furthermore, we have found an inhibitor that inhibits the H3-clipping activity of GDH. Like previously reported proteases, GDH too may have the potential to regulate/modulate post-translational modifications of histone H3 by removing the N-terminal residues of the histone. In short, our findings identify an unexpected proteolytic activity of GDH specific to histone H3 that is regulated by redox state, ionic concentrations, and a cellular inhibitor in vitro.</p>
},
	keywords = {Amino Acid Sequence, Animals, Binding Sites, Brain, Chickens, Chromatin, Cysteine Proteases, Disulfides, Epigenesis, Genetic, Gene Expression Regulation, Enzymologic, Glutamate Dehydrogenase, Histones, Hydrogen-Ion Concentration, Liver, Mass Spectrometry, Mice, Molecular Sequence Data, Rats, Recombinant Proteins, Salts, Sulfhydryl Compounds, Temperature},
	issn = {1083-351X},
	doi = {10.1074/jbc.M113.462531},
	author = {Mandal, Papita and Verma, Naveen and Chauhan, Sakshi and Tomar, Raghuvir S}
}
