Sequence elements upstream of the core promoter are necessary for full transcription of the capsule gene operon in Streptococcus pneumoniae strain D39.
Streptococcus pneumoniae is a major bacterial pathogen in humans. Its polysaccharide capsule is a key virulence factor that 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 cotranscribed from a major transcription start site at the -25 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-bp sequence immediately upstream of the core promoter. Unmarked deletions of these promoter elements in the D39 genome also led to significant reduction in CPS production and virulence in mice. Lastly, common cps gene (cps2ABCD) mutants did not show significant abnormality in cps transcription, although they produced significantly less CPS, indicating that the CpsABCD proteins are involved in the encapsulation of S. pneumoniae in a posttranscriptional manner. This study has yielded important information on the transcriptional characteristics of the cps locus in S. pneumoniae.
Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing, China.
Zhensong
Z
Wen
Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York, USA.
Odeniel
O
Sertil
Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing, China.
Yongxin
Y
Cheng
Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing, China.
Shanshan
S
Zhang
Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing, China.
Xue
X
Liu
Biomedical Science and Engineering Center, Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsinchu, Taiwan.
Wen-Ching
WC
Wang
Center for Infectious Disease Research, School of Medicine, Tsinghua University, Beijing, China Collaborative Innovation Center for Biotherapy, Tsinghua University, Beijing, China Collaborative Innovation Center for Biotherapy, State Key Laboratory of Biotherapy and Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, China zhanglab@tsinghua.edu.cn.
Jing-Ren
JR
Zhang
D000818:Animals; D016667:Bacterial Capsules / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins; D051379:Mice; D009876:Operon; D011008:Pneumococcal Infections / Q000382:microbiology / Q000473:pathology; D012045:Regulatory Sequences, Nucleic Acid; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism
D008565:Membrane Proteins; D037521:Virulence Factors; C464998:core protein, mouse