Antisense RNA-dependent transcription termination sites that modulate lysogenic development of satellite phage P4

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Bacteriophage P4 replication genes are repressed during lysogeny via premature transcription termination.
• A small, untranslated bacteriophage P4 CI RNA acts as an antisense RNA, mediating termination by binding to seqA and seqC sequences.
• A Rho-dependent termination site, timm, is known to regulate P4 replication gene expression.

Purpose of the Study:

• To characterize two novel transcription terminators, t1 and t4, involved in bacteriophage P4 gene regulation.
• To elucidate the roles of these terminators and CI RNA in controlling gene expression during the lysogenic state.
• To investigate the necessity of t1 and timm terminators for P4 lysogeny.

Main Methods:

• Utilized bacteriophage PhiR73 as a cloning vector.
• Employed suppressor tRNAGly as a reporter gene to characterize terminator function.
• Performed in vitro assays to assess the interaction between CI RNA and terminator sites.

Main Results:

• Identified and characterized two new terminators, t1 (Rho-independent) and t4 (Rho-independent structure).
• Demonstrated that CI RNA and the seqA target sequence are crucial for efficient termination at t1.
• Found that neither t1 nor timm terminators are essential for lysogeny, but t4 is key for repressing lytic genes in the lysogenic state.

Conclusions:

• The t1 terminator plays a role in CI RNA autoregulation.
• The t4 terminator is the primary site responsible for preventing lytic gene expression during lysogeny.
• Bacteriophage P4 employs a complex system of Rho-dependent and independent terminators, regulated by CI RNA, to control its life cycle.