Abortive initiation occurs prior to promoter clearance. 
# RNA polymerase binds to promoter DNA to form an RNA polymerase-promoter closed complex
# RNA polymerase then unwinds one turn of DNA surrounding the transcription start site to yield an RNA polymerase-promoter open complex
# RNA polymerase enters into abortive cycles of synthesis and releases short RNA products (contains less than 10 nucleotides)
# RNA polymerase escapes the promoter and enters into the elongation step of transcription