1 - Escherichia coli Ribonucleases: Paradigms for Understanding Cellular RNA Metabolism and Regulation

Abstract

This chapter discusses use of Escherichia coli for understanding cellular RNA metabolism and regulation. E. coli has been informative of the mechanisms of synthesis, maturation, function, and decay of RNA. Molecular genetic studies of E. coli and the coliphages show that RNA is the information link between DNA and protein, and that RNA processing is carried out by specific enzymes. The sequencing E. coli, like all other cells, makes a major commitment to RNA synthesis. Approximately 20% of the cell dry mass is RNA, most of which is ribosomal RNA (∼81%) and tRNA (∼14%). The most metabolically labile fraction is mRNA, which comprises only 4% of the RNA. This chapter discusses about E. coli ribonucleases. It explains concepts related to ribonuclease P and ribonucleases HI and HII. It also describes exoribonucleases and polynucleotide phosphorylase. An overview of ribonuclease activity associated with RNA polymerase is presented. The chapter elaborates in detail about ribonucleases involved in ribosomal RNA maturation, and ribonucleases involved in messenger RNA maturation and turnover. The chapter concludes with a discussion on ribonuclease regulation and RNA metabolic control.