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Identification and characterization of cis ‐ and trans ‐acting elements involved in prophage induction in S treptococcus thermophilus J 34
Author(s) -
Koberg Sabrina,
Mohamed Mazhar Desouki Ali,
Faulhaber Katharina,
Neve Horst,
Heller Knut J.
Publication year - 2015
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13140
Subject(s) - biology , lysogenic cycle , prophage , genetics , gene , repressor , lytic cycle , operon , promoter , bacteriophage , microbiology and biotechnology , mutant , gene expression , escherichia coli , virus
Summary The genetic switch region of temperate S treptococcus thermophilus phage TP ‐ J 34 contains two divergently oriented promoters and several predicted operator sites. It separates lytic cycle‐promoting genes from those promoting lysogeny. A polycistronic transcript comprises the genes coding for repressor C rh, metalloproteinase‐motif protein R ir and superinfection exclusion lipoprotein Ltp. Weak promoters effecting monocistronic transcripts were localized for ltp and int (encoding integrase) by N orthern blot and 5′‐ RACE‐PCR . These transcripts appeared in lysogenic as well as lytic state. A polycistronic transcript comprising genes coh (encoding C ro homolog), ant (encoding putative antirepressor), orf7 , orf8 and orf9 was only detected in the lytic state. Four operator sites, of which three were located in the intergenic regions between crh and coh , and one between coh and ant , were identified by competition electromobility shift assays. Cooperative binding of C rh to two operator sites immediately upstream of coh could be demonstrated. Coh was shown to bind to the operator closest to crh only. Oligomerization was proven by cross‐linking C rh by glutaraldehyde. Knock‐out of rir revealed a key role in prophage induction. Rir and C rh were shown to form a complex in solution and Rir prevented binding of C rh to its operator sites.