Structural and functional analysis of YopR and identification of an additional key component of the SPβ phage lysis-lysogeny management system

Abstract

Prophages need to tightly control their lifestyle to either be maintained within the host genome or enter the lytic cycle. The SPβ prophage present in the genome ofBacillus subtilis168 was recently shown to possess anarbitriumsystem defining its replication stage. Using an historicB. subtilisstrain harboring the heat-sensitive SPβ c2 mutant, we analyzed a key component of the lysis-lysogeny decision system called YopR, which is crucial for maintenance of lysogeny. Here, we demonstrate that the heat-sensitive SPβ c2 phenotype is due to a single nucleotide exchange in theyopRgene, rendering the encoded YopRG136Eprotein temperature sensitive. Structural characterization of YopR revealed that the protein is a DNA-binding protein with an overall fold like tyrosine recombinases. Biochemical and functional analyses indicate that YopR has lost the recombinase function and the G136E exchange impairs its higher order structure and DNA binding activity. We also show that the serine recombinase SprA and its accessory factor SprB are not required for the heat-dependent induction of the lytic cycle of the SPβ c2 prophage. Finally, an evolution experiment with aB. subtilisstrain carrying SPβ c2 identified YosL as a novel component of the lysis-lysogeny management system, as the presence ofyosLis crucial for the induction of the lytic cycle of SPβ.

Characterization of a FourU RNA Thermometer in the 5′ Untranslated Region of Autolysin Gene blyA in the Bacillus subtilis 168 Prophage SPβ

“…The prophage SPβ contains the open reading frame for blyA , which plays a crucial role in the lytic activity of the phage in the host cell . SPβ integrates into the genome of its bacterial host and has been found to be ubiquitous in B. subtilis 168. , SPβ is a lysogenic phage with a temperature-dependent lytic life cycle in B. subtilis 168. ,, Previous studies have demonstrated that the level of expression of blyA in B. subtilis 168 increases at high temperatures, and its heat-induced expression is necessary for the lysis of the host cell . Although it is known that heat stress induces the expression of blyA and the proliferation of the SPβ prophage in B. subtilis 168, the underlying molecular mechanism that drives this process has yet to be elucidated.…”

“… 11 , 12 SPβ is a lysogenic phage with a temperature-dependent lytic life cycle in B. subtilis 168. 10 , 13 , 14 Previous studies have demonstrated that the level of expression of blyA in B. subtilis 168 increases at high temperatures, and its heat-induced expression is necessary for the lysis of the host cell. 10 Although it is known that heat stress induces the expression of blyA and the proliferation of the SPβ prophage in B. subtilis 168, 10 the underlying molecular mechanism that drives this process has yet to be elucidated.…”