title: IS6110 functions as a mobile, monocyte-activated promoter in Mycobacterium tuberculosis.
abstract: The mobile insertion sequence, IS6110, is an important marker in tracking of Mycobacterium tuberculosis strains. Here, we demonstrate that IS6110 can upregulate downstream genes through an outward-directed promoter in its 3' end, thus adding to the significance of this element. Promoter activity was orientation dependent and was localized within a 110 bp fragment adjacent to the right terminal inverted repeat. Transcripts from this promoter, named OP6110, begin approximately 85 bp upstream of the 3' end of IS6110. Use of green fluorescent protein (GFP) expression constructs showed that OP6110 was upregulated in M. tuberculosis during growth in human monocytes and in late growth phases in broth. Analysis of natural insertion sites in M. tuberculosis showed that IS6110 upregulated expression of several downstream genes during growth in human monocytes, including Rv2280 in H37Rv and the PE-PGRS gene, Rv1468c, in the clinical strain 210, which is a member of the Beijing family. Transcription between IS6110 and downstream genes was confirmed by reverse transcription polymerase chain reaction. The ability to activate genes during infection suggests that IS6110 has the potential to influence growth characteristics of different strains, and indicates another mechanism by which IS6110 can impact M. tuberculosis evolution.
authors.affiliation: Department of Microbiology, Center for Pulmonary and Infectious Disease Control, University of Texas Health Center at Tyler, 11937 US Highway 271, Tyler, TX 75708-3154, USA.
authors.forename: Hassan
authors.initials: H
authors.lastname: Safi
authors.forename: Peter F
authors.initials: PF
authors.lastname: Barnes
authors.forename: David L
authors.initials: DL
authors.lastname: Lakey
authors.forename: Homayoun
authors.initials: H
authors.lastname: Shams
authors.forename: Buka
authors.initials: B
authors.lastname: Samten
authors.forename: Ramakrishna
authors.initials: R
authors.lastname: Vankayalapati
authors.forename: Susan T
authors.initials: ST
authors.lastname: Howard
mesh_terms: D019677:Artificial Gene Fusion; D002460:Cell Line; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D009000:Monocytes / Q000382:microbiology*; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D012333:RNA, Messenger / Q000032:analysis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020079:Terminal Repeat Sequences; D024363:Transcription Initiation Site; D015854:Up-Regulation
chemical_list: D004251:DNA Transposable Elements; D008164:Luminescent Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins