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Published June 25, 1985 | Published
Journal Article Open

Preferential localization of variant nucleosomes near the 5'-end of the mouse dihydrofolate reductase gene


We have probed the structure of nucleosomes within the 31-kilobase pair long, transcriptionally active gene for dihydrofolate reductase (DHFR) in mouse cells which contain multiple copies of the DHFR gene. We found that the distribution of electrophoretically variant nucleosomes within the DHFR gene is highly nonuniform: variant DHFR nucleosomes are abundant within and in the immediate vicinity of the approximately 200-base pair (bp) long first DHFR exon, and decrease by at least 10-fold within two nucleosomes upstream and downstream from this region. The nonuniformly distributed variant DHFR mononucleosomes are of two electrophoretically distinguishable discrete types. One corresponds to a mononucleosome containing a approximately 180-bp DNA fragment and possibly also histone H1 and high mobility group proteins. The other type of variant DHFR mononucleosome contains a approximately 146-bp DNA fragment, and its changes in relative content within the DHFR gene closely parallel those of the 180-bp variant mononucleosome. Several lines of evidence are consistent with the interpretation that the electrophoretically variant approximately 146-bp (core) mononucleosome species corresponds to diubiquitinated DHFR nucleosomes. We discuss possible causal relationships between the observed nonuniform distribution of variant nucleosomes within the DHFR gene and the DHFR gene transcription.

Additional Information

© 1985 ASBMB. Currently published by Elsevier Inc; originally published by American Society for Biochemistry and Molecular Biology. User License: Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0). We are greatly indebted to Robert Schimke and Gray Crouse for the DHFR DNA clones. We also thank Mark Solomon, Paul Swerdlow, and especially Daniel Finley for helpful comments on the manuscript, and Barbara Doran for secretarial assistance. This work was supported by grants (to A. V.) from the National Institute of General Medical Sciences (GM31530) and from the W. Grace & Company. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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Published - J._Biol._Chem.-1985-Barsoum-7688-97.pdf


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