Initiation step of transcription is simply binding of RNA polymerase on the DNA strand and its activation by addition of a phosphate group onto it.
Different kind of promotors are present close to the transcription starting site and different kind of transcription factors (TFIID ,TFIIB ...) are present binding onto promotors making the RNA polymerase bind onto DNA.
is there different types of RNA polymerase II ? I know that it is RNA Polymerase II which is responsible for mRNA formation but my question is; is RNA Polymerase II further subdivided according to what kind of protein will be synthesised after translation? otherwise why do different kinds of transcription factors exist?