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Sci Adv. 2016 Nov 11;2(11):e1601865. eCollection 2016 Nov.

Overcoming a nucleosomal barrier to replication.

Author information

1
Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
2
Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
3
Fox Chase Cancer Center, Philadelphia, PA 19111, USA.; Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.

Abstract

Efficient overcoming and accurate maintenance of chromatin structure and associated histone marks during DNA replication are essential for normal functioning of the daughter cells. However, the molecular mechanisms of replication through chromatin are unknown. We have studied traversal of uniquely positioned mononucleosomes by T7 replisome in vitro. Nucleosomes present a strong, sequence-dependent barrier for replication, with particularly strong pausing of DNA polymerase at the +(31-40) and +(41-65) regions of the nucleosomal DNA. The exonuclease activity of T7 DNA polymerase increases the overall rate of progression of the replisome through a nucleosome, likely by resolving nonproductive complexes. The presence of nucleosome-free DNA upstream of the replication fork facilitates the progression of DNA polymerase through the nucleosome. After replication, at least 50% of the nucleosomes assume an alternative conformation, maintaining their original positions on the DNA. Our data suggest a previously unpublished mechanism for nucleosome maintenance during replication, likely involving transient formation of an intranucleosomal DNA loop.

KEYWORDS:

Replication; chromatin; mechanism; nucleosome

PMID:
27847876
PMCID:
PMC5106197
DOI:
10.1126/sciadv.1601865
[Indexed for MEDLINE]
Free PMC Article

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