Switch from [thetas] to sigma replication of bacteriophage lambda DNA: factors involved in the process and a model for its regulation

Bacteriophage lambda genome is one of the classical model replicons in studies on the regulation of DNA replication. Moreover, since genes coding for Shiga toxins are located in genomes of lambdoid phages, understanding of mechanisms controlling lambda DNA replication may be of bio-medical importanc...

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Bibliographic Details
Published in:Molecular genetics and genomics : MGG 2007-07, Vol.278 (1), p.65-74
Main Authors: Narajczyk, Magdalena, Baranska, Sylwia, Wegrzyn, Alicja, Wegrzyn, Grzegorz
Format: Article
Language:English
Subjects:
Bacteria
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Summary:Bacteriophage lambda genome is one of the classical model replicons in studies on the regulation of DNA replication. Moreover, since genes coding for Shiga toxins are located in genomes of lambdoid phages, understanding of mechanisms controlling lambda DNA replication may be of bio-medical importance. During lytic development of bacteriophage lambda , its genome is replicated according to the [thetas] (circle-to-circle) mode early after infection, and then it is switched to the sigma (rolling circle) mode. Two mechanisms of regulation of this switch were proposed recently and both suggested a crucial role for directionality of lambda DNA replication. Whereas one hypothesis assumed transient impairment of ClpP/ClpX-mediated proteolysis of the lambda O initiator protein, another suggested a crucial role for transcriptional activation of the ori lambda region and factors involved in the control of the p sub(R) promoter activity. Here we demonstrate that mutations in clpP and clpX genes had little influence on both directionality of lambda DNA replication and appearance of sigma replication intermediates. On the other hand, regulators affecting activity of the p sub(R) promoter (responsible for initiation of transcription, which activates ori lambda ) directly or indirectly influenced directionality of lambda DNA replication to various extents. Therefore, we conclude that regulation of the efficiency of transcriptional activation of ori lambda , rather than transient impairment of the lambda O proteolysis, is responsible for the control of the switch from [thetas] to sigma replication, and propose a model for this control.
ISSN:1617-4615
1617-4623
DOI:10.1007/s00438-007-0228-y