A statistical-mechanical model for regulation of long-range chromatin structure and gene expression.
In eukaryotic organisms, organization of chromatin is considered to play a role in transcriptional regulation by limiting the accessibility of a gene to the transcription machinery. It is not fully understood, however, how chromatin around a particular locus can be specifically altered to allow transcription. This paper introduces a statistical-mechanical model of chromatin to illustrate a potential mechanism. The model, which is mathematically equivalent to the one-dimensional Ising model of magnetic systems, explains how gene regulatory DNA sequences can affect the chromatin structure over a long distance in cis. The main assumption of the model is cooperativity of histone H1 in binding to the nucleosome array. This cooperativity results in a long-range correlation of histone H1 distribution along the chromatin. Due to this long-range correlation, a gene regulatory element, such as a transcriptional enhancer, may lead to depletion of histone H1 over a large region of chromatin thereby increasing the accessibility of the gene. The model provides a mechanism for a sensitive genetic switch and explains several aspects of gene regulation and chromatin structure.
Ishii
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Graduate Program in Biophysics and Structural Biology, MS 008, Brandeis University, 415 South St., Waltham, MA 02454-9110, USA.
D000818:Animals; D002843:Chromatin; D004247:DNA; D005057:Eukaryotic Cells / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D006657:Histones / Q000378:metabolism; D008957:Models, Genetic; D015233:Models, Statistical; D015394:Molecular Structure; D012045:Regulatory Sequences, Nucleic Acid
D002843:Chromatin; D006657:Histones; D004247:DNA