Targeting of high mobility group-14/-17 proteins in chromatin is independent of DNA sequence

Chromosomal proteins high mobility group (HMG)-14 and HMG-17 are nucleosoma l-binding proteins that unfold the chromatin fiber and enhance transcriptio n from chromatin templates. Their intracellular organization is dynamic and related to both cell cycle and transcription. Here we examine possible mec hanisms for targeting HMG-14/-17 to specific regions in chromatin. Chromati n immunoprecipitation assays indicate that HMG-17 protein is not preferenti ally associated with chromatin regions containing transcriptionally active genes, or any type of specific DNA. We used a modification of the random am plified polymorphic DNA method to analyze DNA in various HMG-14/-17 nucleos ome complexes. We found that although HMG-14 or HMG-17 proteins preferentia lly associate with core particles in which the DNA has a low frequency of C G dinucleotides, the genome does not contain consensus sequences that serve as specific targeting sites for the binding of either HMG-14 or HMG-17 pro teins to nucleosomes. We used size exclusion and ion exchange chromatograph y to demonstrate that nuclei contain a large portion of HMG-17 associated w ith other proteins in a multiprotein complex. We suggest that these complex es regulate the dynamic organization of HMG-14/-17 in the nucleus and serve to target the proteins to specific sites in chromatin.