The selective binding of HMG1 to the cruciform DNA structure and the subsequent resumption of transcription.

The binding of DNA binding protein HMG1 to palindromic sequences that can form the cruciform structure in supercoiled DNA and the subsequent effects on the transcription of the sequence were examined. The results show that the cruciform structure formed under negative supercoiling is a block to transcription and that HMG1, which bound selectively to single-stranded region within the cruciform, can remove the block by altering DNA conformation to allow the stalled RNA polymerase at the block to resume transcription.