RNaseE-mediated mRNA degradation as determinant of polarity in phage f1.

RNA processing and degradation are important steps in the regulation of gene expression. The genes present on the DNA of filamentous phage f1 are expressed at very different levels. A group of genes which are expressed at a very low level (genes III, VI, I and IV is located in the region IF of the phage DNA. The current model proposes that expression of the genes III. VI and I (which form an operon) is regulated by readthrough transcription at a weak terminator located at the end of gene III, while that of gene IV by a terminator located at the end of it. In contrast with this, we found that very long transcripts complementary to the entire f1 DNA are synthesized in the infected cells and that they are quickly processed to shorter, mature transcripts. We discovered that these processing events and differential stability of specific transcripts, are the key elements which regulate the expression of these 4 genes.