RNA Polymerases as Molecular Motors

In transcription initiation, RNA polymerase (RNAP) binds to promoter DNA, unwinds a turn of promoter DNA to yield an RNAP-promoter open complex containing an unwound "transcription bubble," and selects a transcription start site (TSS).In the next step of initiation, termed "initial transcription," RNAP remains bound to the promoter and synthesizes an RNA product of a threshold length of approximately 11-15 nucleotides (nt).In the final step of initiation,