Strains of the East Asian (W/Beijing) Lineage ofMycobacterium tuberculosisAre DosS/DosT-DosR Two-Component Regulatory System Natural Mutants

Abstract

As part of our ongoing efforts to uncover the phenotypic consequences of genetic variability among clinical Mycobacterium tuberculosis isolates, we previously reported that isolates of the "East Asian" or "W/Beijing" lineage constitutively overexpress the coordinately regulated transcriptional program known as the DosR regulon under standard in vitro conditions. This phenotype distinguishes the W/Beijing lineage from all other M. tuberculosis lineages, which normally induce expression of this regulon only once exposed to low oxygen or nitric oxide, both of which result in inhibition of bacterial respiration and replication. Transcription of the DosR regulon is controlled through a two-component regulatory system comprising the transcription factor DosR and two possible cognate histidine sensor kinases, DosS and DosT. Through sequence analysis of a carefully selected set of isolates representing each of the major M. tuberculosis lineages, we describe herein a naturally occurring frameshift mutation in the gene encoding the DosT sensor kinase for isolates of the most recently evolved W/Beijing sublineages. Intriguingly, the occurrence of the frameshift mutation correlates precisely with the appearance of the constitutive DosR regulon phenotype displayed by the same "modern" W/Beijing strains. However, complementation studies have revealed that the mutation in dosT alone is not directly responsible for the constitutive DosR regulon phenotype. Our data serve to highlight the evolutionary pressure that exists among distinct M. tuberculosis lineages to maintain tight control over DosR regulon expression.

The Mycobacterium DosR regulon structure and diversity revealed by comparative genomic analysis

“…The initial response to hypoxia of MTB includes the altered expression of about 100 genes, including the DosR regulon. The DosR regulon composes of 48 coregulated genes, putatively essential for Mtb survival during latency [Fallow et al, 2010;Rustad et al, 2009], such as the genes involved in alternative electron transport pathways (fdxA), nitrate metabolism (narK2 and narX), triglyceride synthetase (tgs1), and deoxynucleoside triphosphate synthesis under microaerophilic conditions (nrdZ) [Fallow et al, 2010;Rustad et al, 2009]. The DosR regulon is regulated by a two-component regulatory system consisting of two sensor kinases-DosS (Rv3132c) and DosT (Rv2027c), and a response regulator DosR (Rv3133c).…”

“…Mtb H37Rv and M. canettii dosR expression were upregulated under hypoxia, while DosR expression in Mtb Beijing is lowered, about 53-and 25-fold of the above two strains [Badillo-Lopez et al, 2010]. Interestingly, DosR regulon expression in W/Beijing strain is constitutive under normal conditions, somewhat relevant to a natural frameshift mutation in the DosT gene [Fallow et al, 2010]. However, role of dosT mutation in the constitutive DosR regulon phenotype is controversial [Honaker et al, 2010].…”

“…Both enzyme clusters are involved in the ETS. The capability of W/Beijing strains to constitutively overexpress dosR regulon prior to stimuli such as NO might be the secret for mycobacterium's super surviving ability [Fallow et al, 2010]. The poor protection offered by BCG vaccination against W/Beijing strain might be stemmed from this unique feature.…”

Adaptation to Environmental Stimuli within the Host: Two-Component Signal Transduction Systems of Mycobacterium tuberculosis

“…This may be due to observed differences in dormancy regulon expression between the M. tuberculosis and M. bovis strains (70). Recent evidence also indicates that strains of the highly virulent M. tuberculosis W-Beijing lineage express dosR at elevated levels (3,40,122). Additionally, a large number of isolates sequenced from this lineage contain a frameshift mutation in dosT that results in the introduction of a premature stop codon (40).…”

Perfil transcriptômico comparativo de macrófagos em cultura, infectados com isolados clínicos de Mycobacterium tuberculosis com diferentes perfis de resistência a quimioterápicos

“…O sucesso do bacilo tem sido associado à sua grande capacidade de disseminação, com altas taxas de mortalidade e resistência as drogas. Estudos com estas cepas comprovam a capacidade do bacilo em gerar mortes rápidas em ratos e macrófagos in vitro, corroborando os dados epidemiológicos obtidos até o momento (FALLOW et al, 2010, SALINAS et al, 2005.…”