title: Alternative sigma factor sigmaH modulates prophage integration and excision in Staphylococcus aureus.
abstract: The prophage is one of the most important components of variable regions in bacterial genomes. Some prophages carry additional genes that may enhance the toxicity and survival ability of their host bacteria. This phenomenon is predominant in Staphylococcus aureus, a very common human pathogen. Bioinformatics analysis of several staphylococcal prophages revealed a highly conserved 40-bp untranslated region upstream of the int gene. A small transcript encoding phage integrase was identified to be initiated from the region, demonstrating that the untranslated region contained a promoter for int. No typical recognition sequence for either sigma(A) or sigma(B) was identified in the 40-bp region. Experiments both in vitro and in vivo demonstrated that sigma(H) recognized the promoter and directed transcription. Genetic deletion of sigH altered the int expression, and subsequently, the excision proportion of prophage DNAs. Phage assays further showed that sigH affected the ability of spontaneous lysis and lysogenization in S. aureus, suggesting that sigH plays a role in stabilizing the lysogenic state. These findings revealed a novel mechanism of prophage integration specifically regulated by a host-source alternative sigma factor. This mechanism suggests a co-evolution strategy of staphylococcal prophages and their host bacteria.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Tao
authors.forename: Xiaoqian
authors.initials: X
authors.lastname: Wu
authors.forename: Baolin
authors.initials: B
authors.lastname: Sun
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D019143:Evolution, Molecular; D017353:Gene Deletion; D016679:Genome, Viral; D008242:Lysogeny / Q000502:physiology*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D039002:Prophages / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics*; D013211:Staphylococcus aureus / Q000472:pathogenicity / Q000821:virology*; D014158:Transcription, Genetic / Q000235:genetics; D020506:Untranslated Regions / Q000235:genetics; D014774:Virulence; D014775:Virus Activation / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C120328:SigH protein, bacteria; D012808:Sigma Factor; D020506:Untranslated Regions