T4 Factor Involved in Phage‐induced Host mRNA Degradation

Abstract

ObjectiveIdentification and characterization of T4 factor involved in phage‐induced host mRNA degradationResultsBacteriophage T4 causes a shift of gene expression from host Escherichia coli to T4 immediately after infection. In this process, host mRNAs are rapidly degraded, which may facilitate T4 gene expression by providing precursors for transcription and free ribosomes. Recently we found that the rapid degradation of host mRNAs was partially suppressed and a decay intermediate of lpp mRNA was markedly accumulated in Δ(39‐56)6 phage‐infected cells. Since the 4.6‐kb region missing in Δ(39‐56)6 phage contain 8 orfs, we tested the effect of each orf on host mRNA degradation and found that the causal gene is dda.2, a T4 early gene, located immediate downstream of an early promoter. 
 The average number of phages produced in a cell infected with a deletion mutant of dda.2 (Δdda.2) was one‐third, in comparison to that of wild type, indicating that dda.2 is necessary for efficient propagation of T4. On the other hand, over‐expression of Dda.2 was found to be toxic for cells. With the induction of plasmid‐borne dda.2, cell growth was stopped within 30 min, and cell viability was significantly reduced. In addition, amounts of E. coli mRNAs, such as lpp and ompA were considerably reduced. Furthermore, the decay of ompA and lpp mRNAs was accelerated after induction of plasmid‐borne dda.2.Conclusions1. T4 dda.2 is involved in phage‐induced host mRNA degradation, which is thought to be important to facilitate T4 gene expression.2. T4 dda.2 has a significant role in bacterial physiology probably with a modulation in mRNA metabolism.Source of the research support: The ministry of education, culture, sports, science and technology, Japan