Infect Immun. 2015 Mar 2. pii: IAI.02944-14. [Epub ahead of print]
The sequence elements upstream of the core promoter are necessary for the full transcription of the capsule gene operon in Streptococcus pneumoniae strain D39.
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Abstract
Streptococcus pneumoniae is a major bacterial pathogen in humans. Its polysaccharide capsule is a key virulence factor, which promotes bacterial evasion of human phagocytic killing. While S. pneumoniae produces at least 94 antigenically different types of capsule, the genes for biosynthesis of almost all capsular types are arranged in the same locus. The transcription of the capsular polysaccharide (cps) locus is not well understood. This study determined the transcriptional features of the cps locus in the type-2 virulent strain D39. The initial analysis revealed that the cps genes are co-transcribed from a major transcription start site at the -25th nucleotide G upstream of cps2A, the first gene in the locus. Using unmarked chromosomal truncations and a luciferase-based transcriptional reporter, we showed that the full transcription of the cps genes not only depends on the core promoter immediately upstream of cps2A, but also requires additional elements upstream of the core promoter, particularly a 59-base pair sequence immediately upstream of the core promoter. Unmarked deletion of these promoter elements in the D39 genome also led to significant reduction in CPS production and virulence in mice. Lastly, the mutants of the common cps genes cps2ABCD did not show significant abnormality in the cps transcription although they produced significantly less CPS, indicating that the CpsABCD proteins are involved in the encapsulation of S. pneumoniae in a post-transcriptional manner. This study has yielded important information on the transcriptional characteristics of the cps locus in S. pneumoniae.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
PMID: 25733517 [PubMed - as supplied by publisher]
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