複選題40. The sigma factor (σ) of procaryotic RNA polymerase is part of the core enzyme. Which of the following statement are TRUE for sigma factor? (A)it is released from the core enzyme after first bond has been formed. (B) it is inhibited by o-amanitin (C) it is required for transcription initiation (D) it is dispensable for in vitro RNA polymerization reaction (E) it is a component of RNA polymerase holoenzyme