Gravar-mail: ABORTIVE INITIATION AND PRODUCTIVE INITIATION BY RNA POLYMERASE INVOLVE DNA SCRUNCHING: Single-molecule-nanomanipulation experiments--in which magnetic tweezers are used to monitor RNA-polymerase-induced DNA unwinding with ~1 bp resolution and ~1 s temporal resolution--show that both abortive initiation and productive initiation by RNA polymerase involve DNA “scrunching.”