Abstract
Histone H1 is a major chromatin protein, which stabilizes the nucleosome, has an essential role in organizing nucleosomes into higher order structures, and may have a role as a repressor of transcription (van Holde, K. E. (1989) Chromatin, Springer Publishing Co., New York). Here we show that H1 forms a defined complex with a synthetic four-way junction of DNA strands even in the presence of an excess of linear nonspecific competitor DNA. The four-way junction also competes efficiently against two duplex DNA molecules, which together have the same sequence information as the four-way junction molecule. Another major chromatin protein, high mobility group protein 1, also binds four-way junction structures specifically (Bianchi, M. E., Beltrame, M., and Paonessa, G. (1989) Science 243, 1056-1059), and this similar behavior may indicate a related function of these proteins. Our finding may suggest that four-way DNA junction is a structural equivalent to the main H1 binding site in the nucleosome: a crossover of double helical DNA at the point where the DNA enters and exits the nucleosome (Allan, J., Hartman, P. G., Crane-Robinson, C., and Aviles, F. X. (1980) Nature 288, 675-679).
Highlights
From the Department of Biochemistry a n d Biophysics, Oregon State University, Coruallis, Oregon 97331-7305 ies in our laboratory have demonstrathteadt histone H1 binds preferentiallytocrossovers in superhelical DNA (13)
We show that H1 forms a defined complex with a Synthesis of the Four-way Junctions-We constructed a foursynthetic four-wayjunction of DNA strands even in the presence of an excess of linear nonspecific competitor DNA.The four-way junction competes efficiently against two duplex DNA molecules,which together have the same sequence information as the four-wayjunction molecule.Another major chromatin proteihni,gh mobility group protein 1, binds four-wayjunction structures
Four-way junction DNA is present during genetic recombi
Summary
We show that H1 forms a defined complex with a Synthesis of the Four-way Junctions-We constructed a foursynthetic four-wayjunction of DNA strands even in the presence of an excess of linear nonspecific competitor DNA.The four-way junction competes efficiently against two duplex DNA molecules,which together have the same sequence information as the four-wayjunction molecule.Another major chromatin proteihni,gh mobility group protein 1, binds four-wayjunction structures We constructed control linear DNAs, which together contain the same sequence information as the four-way junction (Fig. 1).The structures were radiolabeledby prelabeling one of the oligonucleotides with y-[32P]ATPusing T4 polynucleotide kinase. Our finding may suggest that four-way DNA junction is a structural equivalent to the main H1 binding site in the nucleosome: a crossover of double helical DNA at the point where the DNA enters and exits the nucleosome
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