Bacteriophage GIL01 is a temperate phage of the virus family Tectiviridae that infects the bacterium Bacillus thuringiensis. While most temperate bacteriophages that enter the active lytic cycle upon DNA damage use their own repressor to maintain the dormant lysogenic cycle, GIL01 uses the bacterial repressor LexA for this purpose. LexA is the master regulator of the bacterial SOS response, which is activated in the event of DNA damage and allows the cell to repair it. GIL01 carries several small proteins with a predicted regulatory function. In this work, we focused on the gp6 and gp7 proteins. The gp6 protein is a homolog of the amino terminal domain of the LexA protein, which, after binding to the P3 promoter region, activates transcription of the late genes of phage GIL01 and activation of the lytic cycle. The gp7 protein forms a complex with the bacterial repressor LexA and enhances its binding to DNA target sequences. The aim of this master thesis was to investigate the influence of the gp6 and gp7 proteins on the P1-P2 promoter region of bacteriophage GIL01, which controls the expression of early genes. Here we show that gp6 is not required for the activation of the P1-P2 promoter region. Our data support the results that the gp7 protein is a co-repressor and, as an isolated recombinant protein, does not freely enter the bacterial cell. Our results suggest that an additional bacteriophage factor is required for the activation of the P1 promoter region. To better characterize the interaction between LexA and gp7 we prepared plasmid constructs for the synthesis of single alanine mutants of gp7. Results of other researchers show that none of the mutants carrying alanine substitution at the carboxy terminal end lost the capability to interact with LexA.
|
