Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 146

It was once assumed that after initiation occurs, the RNA polymerase moves along the DNA at a uniform rate, polymerizing nucleotides into RNA. However, it is now known that the RNA polymerase often starts making RNA and then repeatedly aborts, synthesizing a number of short RNAs in a process called abortive initiation before finally leaving the promoter. Even after transcription is under way, RNA polymerase often pauses and sometimes even backs up before continuing. In this section, we discuss in more detail each of the steps in transcription (Figure 2.8), which have been established over many years by a large number of researchers. We discuss these steps one at a time because each of them is the basis for regulatory mechanisms that are discussed in later chapters.