Nucleosome core binding region of chromosomal protein HMG-17 acts as an independent functional domain.
Chromosomal proteins HMG-14 and HMG-17 have a modular structure. Here we examine whether the putative nucleosome-binding domain in these proteins can function as an independent module. Mobility shift assays with recombinant HMG-17 indicate that synthetic molecules can be used to analyze the interaction of this protein with the nucleosome core. Peptides corresponding to various regions of the protein have been synthesized and their interaction with nucleosome cores analyzed by mobility shift, thermal denaturation and DNase I digestion. A 30 amino acid long peptide, corresponding to the putative nucleosome-binding domain of HMG-17, specifically shifts the mobility of cores as compared to free DNA, elevates the tm of both the premelt and main melt of the cores and protects from DNase I digestion the same nucleosomal DNA sites as the intact protein. The binding of both the peptide and the intact protein is lost upon digestion of the histone tails by trypsin. The nucleosomal binding sites of the peptide appear identical to those of the intact protein. Thus, a region of the protein can acts as an independent functional domain. This supports the notion that HMG-14 and HMG-17 are modular proteins. This finding is relevant to the understanding of the function and evolution of HMG-14/-17, the only nucleosome core particle binding proteins known to date.
Crippa
M P
MP
Laboratory of Molecular Carcinogenesis National Cancer Institute, National Institutes of Health Bethesda, MD 20892.
Alfonso
P J
PJ
Bustin
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D005075:Biological Evolution; D003850:Deoxyribonuclease I; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013552:Swine; D013816:Thermodynamics
D006609:High Mobility Group Proteins; D009707:Nucleosomes; D010455:Peptides; D011994:Recombinant Proteins; D003850:Deoxyribonuclease I