%0 Journal Article %A Piazzolla, D. %A Calì, S. %A Spoldi, E. %A Forti, F. %A Sala, C. %A Magnoni, F. %A Dehò, G. %A Ghisotti, D. %T Expression of phage P4 integrase is regulated negatively by both Int and Vis %D 2006 %J Journal of General Virology, %V 87 %N 8 %P 2423-2431 %@ 1465-2099 %R https://doi.org/10.1099/vir.0.81875-0 %I Microbiology Society, %X Phage P4 int gene encodes the integrase responsible for phage integration into and excision from the Escherichia coli chromosome. Here, the data showing that P4 int expression is regulated in a complex manner at different levels are presented. First of all, the Pint promoter is regulated negatively by both Int and Vis, the P4 excisionase. The N-terminal portion of Int appears to be sufficient for such a negative autoregulation, suggesting that the Int N terminus is implicated in DNA binding. Second, full-length transcripts covering the entire int gene could be detected only upon P4 infection, whereas in P4 lysogens only short 5′-end covering transcripts were detectable. On the other hand, transcripts covering the 5′-end of int were also very abundant upon infection. It thus appears that premature transcription termination and/or mRNA degradation play a role in Int-negative regulation both on the basal prophage transcription and upon infection. Finally, comparison between Pint–lacZ transcriptional and translational fusions suggests that Vis regulates Int expression post-transcriptionally. The findings that Vis is also an RNA-binding protein and that Int may be translated from two different start codons have implications on possible regulation models of Int expression. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.81875-0