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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

CovR and VicRKX Regulate Transcription of the Collagen Binding Protein Cnm of Streptococcus mutans

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Author(s):
Alves, Livia Araujo [1, 2] ; Ganguly, Tridib [2] ; Mattos-Graner, Renata O. [1] ; Kajfasz, Jessica [2] ; Harth-Chu, Erika N. [1] ; Lemos, Jose A. [2] ; Abranches, Jacqueline [2]
Total Authors: 7
Affiliation:
[1] Univ Estadual Campinas, Piracicaba Dent Sch, Dept Oral Diag, Piracicaba, SP - Brazil
[2] Univ Florida, Coll Dent, Dept Oral Biol, Gainesville, FL 32610 - USA
Total Affiliations: 2
Document type: Journal article
Source: Journal of Bacteriology; v. 200, n. 23 DEC 2018.
Web of Science Citations: 1
Abstract

Cnm is a surface-associated protein present in a subset of Streptococcus mutans strains that mediates binding to extracellular matrices, intracellular invasion, and virulence. Here, we showed that cnm transcription is controlled by the global regulators CovR and VicRKX. In silico analysis identified multiple putative CovR- and VicR-binding motifs in the regulatory region of cnm as well as in the downstream gene pgfS, which is associated with the posttranslational modification of Cnm. Electrophoretic mobility shift assays revealed that CovR and VicR specifically and independently bind to the crim and pgfS promoter regions. Quantitative real-time PCR and Western blot analyses of Delta covR and Delta vicK strains as well as of a strain overexpressing vicRKX revealed that CovR functions as a positive regulator of cnm, whereas VicRKX acts as a negative regulator. In agreement with the role of VicRKX as a repressor, the Delta vicK strain showed enhanced binding to collagen and laminin and higher intracellular invasion rates. Overexpression of vicRKX was associated with decreased rates of intracellular invasion but did not affect collagen or lamin binding activities, suggesting that this system controls additional genes involved in binding to these extracellular matrix proteins. As expected, based on the role of CovR in cnrn regulation, the Delta covR strain showed decreased intracellular invasion rates, but, unexpectedly collagen and laminin binding activities were increased in this mutant strain. Collectively, the results presented here expand the repertoire of virulence-related genes regulated by CovR and VicRKX to include the core gene pgfS and the noncore gene cnm. IMPORTANCE Streptococcus mutans is a major pathogen associated with dental caries and also implicated in systemic infections, in particular, infective endocarditis. The Cnm adhesin of S. mutans is an important virulence factor associated with systemic infections and caries severity. Despite its role in virulence, the regulatory mechanisms governing cnm expression are poorly understood. Here, we describe the identification of two independent regulatory systems controlling the transcription of cnm and the downstream pgfS-pgfM1-pgfE-pgfM2 operon. A better understanding of the mechanisms controlling expression of virulence factors like Cnm can facilitate the development of new strategies to treat bacterial infections. (AU)

FAPESP's process: 15/12940-3 - Identification of surface proteins of Streptococcus mutans involved in evasion of opsonization by the complement system
Grantee:Renata de Oliveira Mattos Graner
Support type: Regular Research Grants
FAPESP's process: 16/17216-4 - Analysis of the functions of pepO protein in systemic virulence of Streptococcus mutans
Grantee:Lívia Araújo Alves
Support type: Scholarships abroad - Research Internship - Doctorate
FAPESP's process: 15/07237-1 - Identification of surface proteins of Streptococcus mutans involved in the scape to opsonization by the complement system
Grantee:Lívia Araújo Alves
Support type: Scholarships in Brazil - Doctorate