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J Bacteriol

Title:		"Transient association of an alternative sigma factor, ComX, with RNA polymerase during the period of competence for genetic transformation in Streptococcus pneumoniae"
Author(s):		Luo P; Morrison DA;
Address:		"Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, 900 S. Ashland Avenue, Chicago, IL 60607, USA"
Journal Title:		J Bacteriol
Year:		2003
Volume:		185
Issue:		1
Page Number:		349 - 358
DOI:		10.1128/JB.185.1.349-358.2003
ISSN/ISBN:		0021-9193 (Print) 1098-5530 (Electronic) 0021-9193 (Linking)
Abstract:		"Natural transformation in Streptococcus pneumoniae is regulated by a quorum-sensing system that acts through accumulation and sensing of a peptide pheromone (competence-stimulating peptide [CSP]) to control many competence-specific genes acting in DNA uptake, processing, and integration. The period of competence induced by CSP lasts only 15 min (quarter-height peak width). The recently identified regulator ComX is required for the CSP-dependent expression of many competence-specific genes that share an unusual consensus sequence (TACGAATA) at their promoter regions. To test the hypothesis that this regulator acts as a transient alternative sigma factor, ComX was purified from an Escherichia coli overexpression strain and core RNA polymerase was purified from a comX-deficient S. pneumoniae strain. The reconstituted ComX-polymerase holoenzyme produced transcripts for the competence-specific genes ssbB, cinA, cglA, celA, and dalA and was inhibited by anti-ComX antibody, but not by anti-sigma(70) antibody. Western blotting using antibodies specific for ComX, sigma(70), and poly-His revealed a transient presence of ComX for a period of 15 to 20 min after CSP treatment, while RNA polymerase remained at a constant level and sigma(A) remained between 60 and 125% of its normal level. ComX reached a molar ratio to RNA polymerase of at least 1.5. We conclude that ComX is unstable and acts as a competence-specific sigma factor"
Keywords:		"Amino Acid Sequence Bacterial Proteins/chemistry/metabolism/pharmacology DNA-Directed RNA Polymerases/*metabolism Gene Expression Regulation, Bacterial Molecular Sequence Data Sigma Factor/genetics/*metabolism Streptococcus pneumoniae/*genetics/growth & d;"
Notes:		"MedlineLuo, Ping Morrison, Donald A eng Research Support, U.S. Gov't, Non-P.H.S. 2002/12/18 J Bacteriol. 2003 Jan; 185(1):349-58. doi: 10.1128/JB.185.1.349-358.2003"