Polycysteine-encoding leaderless short ORFs function as cysteine-responsive attenuators of operonic gene expression in mycobacteria.
Mol Microbiol
; 114(1): 93-108, 2020 07.
Article
em En
| MEDLINE
| ID: mdl-32181921
ABSTRACT
Genome-wide transcriptomic analyses have revealed abundant expressed short open reading frames (ORFs) in bacteria. Whether these short ORFs, or the small proteins they encode, are functional remains an open question. One quarter of mycobacterial mRNAs are leaderless, beginning with a 5'-AUG or GUG initiation codon. Leaderless mRNAs often encode unannotated short ORFs as the first gene of a polycistronic transcript. Here, we show that polycysteine-encoding leaderless short ORFs function as cysteine-responsive attenuators of operonic gene expression. Detailed mutational analysis shows that one polycysteine short ORF controls expression of the downstream genes. Our data indicate that ribosomes stalled in the polycysteine tract block mRNA structures that otherwise sequester the ribosome-binding site of the 3'gene. We assessed endogenous proteomic responses to cysteine limitation in Mycobacterium smegmatis using mass spectrometry. Six cysteine metabolic loci having unannotated polycysteine-encoding leaderless short ORF architectures responded to cysteine limitation, revealing widespread cysteine-responsive attenuation in mycobacteria. Individual leaderless short ORFs confer independent operon-level control, while their shared dependence on cysteine ensures a collective response mediated by ribosome pausing. We propose the term ribulon to classify ribosome-directed regulons. Regulon-level coordination by ribosomes on sensory short ORFs illustrates one utility of the many unannotated short ORFs expressed in bacterial genomes.
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Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Peptídeos
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Regulação Bacteriana da Expressão Gênica
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Fases de Leitura Aberta
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Mycobacterium smegmatis
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Elementos de Resposta
Idioma:
En
Revista:
Mol Microbiol
Assunto da revista:
BIOLOGIA MOLECULAR
/
MICROBIOLOGIA
Ano de publicação:
2020
Tipo de documento:
Article
País de afiliação:
Estados Unidos