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Regulation of imm gene expression in bacteriophage T4-infected cells
Abstract:
Two polypeptides (imm-a and imm-b) which are not induced by an immunity mutant T4Dimm2 but by a wild-type strain T4D were identified by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis. Their mol. wt. were 77 000 and 45 000, respectively. These polypeptides exhibited a similar kinetic pattern of synthesis. Within a few minutes p.i. the primary phage established the system that inhibited imm gene expression of superinfecting phage. This was shown by measuring both the phenotypic expression of immunity and the synthesis of imm gene polypeptides. The expression of two other immediate-early genes, namely genes s and 30, and early gene 33, was not affected by primary infection.
Insights
Wild-type T4D phage infection inhibits superinfecting phage immunity gene expression. This inhibition involves two specific polypeptides, imm-a and imm-b, synthesized shortly after primary infection.
Area of Science:
- Molecular biology
- Bacteriophage genetics
- Protein synthesis
Background:
- Bacteriophage T4D exhibits immunity mechanisms to control superinfection.
- The genetic basis and molecular players of T4D immunity are not fully elucidated.
Purpose of the Study:
- To identify polypeptides involved in T4D phage immunity.
- To investigate the kinetics of immunity gene expression during T4D infection.
Main Methods:
- Sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis to identify and characterize polypeptides.
- Measurement of phenotypic immunity expression.
- Analysis of imm gene polypeptide synthesis post-infection (p.i.).
Main Results:
- Two polypeptides, imm-a (77,000 mol. wt.) and imm-b (45,000 mol. wt.), were identified and synthesized following wild-type T4D infection.
- These polypeptides showed similar synthesis kinetics.
- Primary T4D infection rapidly inhibited the expression of immunity genes in superinfecting phages.
- Expression of immediate-early genes (s, 30) and an early gene (33) remained unaffected.
Conclusions:
- Wild-type T4D phage infection induces polypeptides that actively suppress superinfecting phage immunity.
- This suppression mechanism is rapid and specific to immunity gene expression, not affecting other phage genes.