Direct cell-cell contact activates SigM to express the ESX-4 secretion system in Mycobacterium smegmatis.
Proc Natl Acad Sci U S A
; 115(28): E6595-E6603, 2018 07 10.
Article
em En
| MEDLINE
| ID: mdl-29941598
ABSTRACT
Conjugal cell-cell contact between strains of Mycobacterium smegmatis induces the esxUT transcript, which encodes the putative primary substrates of the ESAT-6 secretion system 4 (ESX-4) secretion system. This recipient response was required for conjugal transfer of chromosomal DNA from the donor strain. Here we show that the extracytoplasmic σ factor, SigM, is a cell contact-dependent activator of ESX-4 expression and is required for conjugal transfer of DNA in the recipient strain. The SigM regulon includes genes outside the seven-gene core esx4 locus that we show are also required for conjugation, and we show that some of these SigM-induced proteins likely function through ESX-4. A fluorescent reporter revealed that SigM is specifically activated in recipient cells in direct contact with donor cells. Coculture RNA-seq experiments indicated that SigM regulon induction occurred early and before transconjugants are detected. This work supports a model wherein donor contact with the recipient cell surface inactivates the transmembrane anti-SigM, thereby releasing SigM. Free SigM induces an extended ESX-4 secretion system, resulting in changes that facilitate chromosomal transfer. The contact-dependent inactivation of an extracytoplasmic σ-factor that tightly controls ESX-4 activity suggests a mechanism dedicated to detect, and appropriately respond to, external stimuli from mycobacteria.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
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Fatores de Transcrição
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Regulação Bacteriana da Expressão Gênica
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Conjugação Genética
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Mycobacterium smegmatis
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Sistemas de Secreção Tipo IV
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Sistemas de Secreção Tipo VII
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
2018
Tipo de documento:
Article