Bradyrhizobium japonicum HmuP is an RNA-binding protein that positively controls hmuR operon expression by suppression of a negative regulatory RNA element in the 5' untranslated region.
Mol Microbiol
; 121(6): 1217-1227, 2024 06.
Article
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| MEDLINE
| ID: mdl-38725184
ABSTRACT
The hmuR operon encodes proteins for the uptake and utilization of heme as a nutritional iron source in Bradyrhizobium japonicum. The hmuR operon is transcriptionally activated by the Irr protein and is also positively controlled by HmuP by an unknown mechanism. An hmuP mutant does not express the hmuR operon genes nor does it grow on heme. Here, we show that hmuR expression from a heterologous promoter still requires hmuP, suggesting that HmuP does not regulate at the transcriptional level. Replacement of the 5' untranslated region (5'UTR) of an HmuP-independent gene with the hmuR 5'UTR conferred HmuP-dependent expression on that gene. Recombinant HmuP bound an HmuP-responsive RNA element (HPRE) within the hmuR 5'UTR. A 2 nt substitution predicted to destabilize the secondary structure of the HPRE abolished both HmuP binding activity in vitro and hmuR expression in cells. However, deletion of the HPRE partially restored hmuR expression in an hmuP mutant, and it rescued growth of the hmuP mutant on heme. These findings suggest that the HPRE is a negative regulatory RNA element that is suppressed when bound by HmuP to express the hmuR operon.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Operón
/
Proteínas Bacterianas
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Regulación Bacteriana de la Expresión Génica
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Proteínas de Unión al ARN
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Bradyrhizobium
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Regiones no Traducidas 5'
Idioma:
En
Revista:
Mol Microbiol
Asunto de la revista:
BIOLOGIA MOLECULAR
/
MICROBIOLOGIA
Año:
2024
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Reino Unido