Antitermination is the prokaryotic cell's aid to fix premature termination of RNA synthesis during the transcription of RNA. It occurs when the RNA polymerase ignores the termination signal and continues elongating its transcript until a second signal is reached. Antitermination provides a mechanism whereby one or more genes at the end of an operon can be switched either on or off, depending on the polymerase either recognizing or not recognizing the termination signal.
Antitermination is used by some phages to regulate progression from one stage of gene expression to the next. The lambda gene N, codes for an antitermination protein (pN) that is necessary to allow RNA polymerase to read through the terminators located at the ends of the immediate early genes. Another antitermination protein, pQ, is required later in phage infection. pN and pQ act on RNA polymerase as it passes specific sites. These sites are located at different relative positions in their respective transcription units.