DNA dynamic flexibility and protein recognition: differential stimulation by bacterial histone-like protein HU.

The abundant E. coli "histone-like" protein HU is shown to be a differential effector of DNA recognition by three diverse control proteins. DNA recognition by lac repressor and catabolite activator protein is greatly stimulated, while specific aroH DNA recognition by trp repressor is inhibited. BaCl2, an agent previously shown to promote DNA bending, mimics the HU effect to give the same qualitative differential stimulation spectrum. The HU activation involves cooperativity, further suggesting that the various DNA bends and distortions induced during assembly of higher order HU:DNA structures are important for the HU stimulation. Thus, E. coli chromosomal DNA regulation is likely strongly influenced by HU protein that may promote a variety of alternative DNA structures that either facilitate or inhibit specific recognition by diverse control proteins.