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Chapter 14 : Overview of Transcription
Bacterial RNA polymerase provides the central model for the transcription elongation complex and its various interesting fates-backtracking and correction by Gre protein-mediated transcript cleavage, transcription termination, and the antitermination controls that were discovered in bacteria. RNA polymerase and its transcription factors have functions beyond their obvious activity to provide RNA molecules to the cell, reflecting the fact that RNA polymerase and the process of transcription must have evolved as DNA arose from the primal RNA world-neither is worth much without the other. There is evidence or informed speculation implicating RNA polymerase and transcription proteins in processes of replication, DNA repair, and cell division. Thus, transcription by RNA polymerase activates the origins of replication of Escherichia coli and phage λ in some structural way independent of the RNA product. Just as transcription and replication coevolved, so did the coordination of chromosome segregation and cell division arise in the context of both. DNA is transcribed as it moves about the cell in an organized fashion during replication. RNA is translated at the same time, causing an added complication when emerging membrane proteins are inserted into the membrane and provide points of fixation for the complex.