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Chang HW , Pandey M , Kulaeva OI , Patel SS , Studitsky VM
Overcoming a nucleosomal barrier to replication
Sci Adv. 2016 Nov;2(11) :e1601865
PMID: 27847876    PMCID: PMC5106197   
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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 Our data suggest a previously unpublished mechanism for nucleosome maintenance during replication, likely involving transient formation of an intranucleosomal DNA loop.
2375-2548 Chang, Han-Wen Pandey, Manjula Kulaeva, Olga I Patel, Smita S Studitsky, Vasily M R01 GM055310/GM/NIGMS NIH HHS/United States R01 GM058650/GM/NIGMS NIH HHS/United States Journal Article United States Sci Adv. 2016 Nov 11;2(11):e1601865. eCollection 2016 Nov.