<prompt> True about sigma factor?Subunit of 50s ribosomeSubunit of DNA polymeraseSubunit of RNA polymeraseInitiates DNA replication  <response>: The basic DNA-dependent RNA polymerase of the bacterium Escherichia coli exists as an approximately 400-kDa core complex consisting of two identical a subunits, two large b, and b subunits, and a o subunit. The core RNA polymerase, bba2o, often termed E, associates with a specific protein factor the sigma factor to form holoenzyme, . Sigma factors have a dual role in the process of promoter recognition; s association with core RNA polymerase decreases its affinity for non-promoter DNA, while simultaneously increasing holoenzyme affinity for promoter DNA. REF: Lippincott book of biochemistry 6th ed. 