Structural and transcriptional properties of different nucleosomal particles containing high mobility group proteins 14 and 17 (HMG 14/17).

Binding of high mobility group (HMG) proteins 14 and 17 (HMG 14/17) to complete nucleosomal cores and to cores lacking one H2A.H2B dimer, the amino-terminal tails of histones, or both one H2A.H2B dimer and the amino-terminal ends of histones is accompanied by an overall stabilization of the particles as determined by thermal denaturation, circular dichroism and DNase I digestion. In spite of the structural stabilization brought about by HMG 14/17, the presence of these proteins causes little effect on the efficiency of the different nucleosomal particles as transcription templates for RNA polymerase II. The nucleosomal particles lacking one H2A.H2B dimer and containing two bound HMG 14/17 molecules are efficient in vitro transcription templates, which allow transcription of the whole length of the DNA present in the particle. These results are consistent with HMG 14/17 being present in active chromatin.