title: EspR, a regulator of the ESX-1 secretion system in Mycobacterium tuberculosis, is directly regulated by the two-component systems MprAB and PhoPR.
abstract: The regulatory mechanisms that control the ESX-1 secretion system, a key player in the pathogenesis of Mycobacterium tuberculosis, have not been fully elucidated. However, factors that regulate the ESX-1 substrate EspA usually affect ESX-1 function. Previous studies showed that espA is directly regulated by the nucleoid-associated protein EspR and the two-component system (TCS) MprAB. The PhoPR TCS also activates espA, but the direct target of PhoP was unknown. In this report, we reveal that EspR is directly regulated by MprA and PhoP-Rv, but not by PhoP-Ra. PhoP-Rv and MprA binding sites in the espR promoter were determined by gel-shift and DNase I footprinting assays, which identified a PhoP-protected region centred approximately 205 bp before the espR start codon and that encompasses MprA Region-1, one of two MprA-protected regions. MprA Region-2 is located approximately 60 bp downstream of MprA Region-1 and overlaps a known EspR binding site. Nucleotides essential for the binding of PhoP and/or MprA were identified through site-directed DNA mutagenesis. Our studies also indicate that MprA Region-2, but not MprA Region-1/PhoP region, is required for the full expression of espR. Recombinant strains carrying mutations at MprA Region-2 exhibited lower transcription levels for espR, espA and espD, and had reduced EspR and EspA levels in cell lysates. These findings indicate that EspR may mediate the regulatory effect of PhoPR and MprAB, and provide more insight into the mechanisms underlying ESX-1 control.
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China Shandong Medicinal Biotechnology Center, Jinan, 250062, PR China.
authors.forename: Guangxiang
authors.initials: G
authors.lastname: Cao
authors.affiliation: Department of Microbiology, University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA.
authors.forename: Susan T
authors.initials: ST
authors.lastname: Howard
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China.
authors.forename: Peipei
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Pulmonary Immunology, University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA.
authors.forename: Xisheng
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China.
authors.forename: Xiu-Lan
authors.initials: XL
authors.lastname: Chen
authors.affiliation: Pulmonary Immunology, University of Texas Health Science Center at Tyler, Tyler, TX 75708, USA.
authors.forename: Buka
authors.initials: B
authors.lastname: Samten
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China pangxiuhua@sdu.edu.cn.
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Pang
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis; C480224:MprA protein, Mycobacterium tuberculosis; C061279:PhoR protein, Bacteria; C061064:PhoP protein, Bacteria; D011494:Protein Kinases; C480223:MprB protein, Mycobacterium tuberculosis