Jayanta
Mukhopadhyay
Alternative
sigma factors of Mycobacterium
tuberculosis
in global gene regulation
The M. tuberculosis
genome encodes ~4000 proteins that include ~180 transcriptional
regulators, 13 sigma factors (sig A - sig M), and 11 two component
systems.
Some of the sigma
factors of M. tuberculosis
respond to environmental stress such as cold
shock, heat shock, hypoxia, iron starvation, surface stress, and
oxidative stress, while others respond to currently unknown
environmental conditions.
Results taken
from quantitative reverse-transcription PCR/microarray technology, and
chromatin immunoprecipitation assay, allowed the partial
characterization of seven sigma factors and proposed consensus
sequences of
six sigma factors.
Comprehensive
characterization of sigma factor binding sites and targets, is
still
lacking.
Hence we aim:
- To determine the
binding specificity
of each of 13 sigma
factors using recombinant Mtb RNA polymerase and SELEX method.
- To identify the
promoters for each sigma factor by comparing its binding specificity
sequence with intergenic regions of Mtb genome.
- To identify the
genes directly regulated by each sigma factor by microarray analysis of
mRNA from in vitro transcription assays with Mtb RNA polymerase and
genomic DNA.