Regulation of Replication Fork Progression Through Histone Supply and Demand

Laboratory of Nuclear Dynamics and Genome Plasticity, UMR218 CNRS/Institut Curie, 26 rue d'Ulm, 75248 Paris cedex 05, France.
Science (Impact Factor: 33.61). 01/2008; 318(5858):1928-31. DOI: 10.1126/science.1148992
Source: PubMed


DNA replication in eukaryotes requires nucleosome disruption ahead of the replication fork and reassembly behind. An unresolved
issue concerns how histone dynamics are coordinated with fork progression to maintain chromosomal stability. Here, we characterize
a complex in which the human histone chaperone Asf1 and MCM2–7, the putative replicative helicase, are connected through a
histone H3-H4 bridge. Depletion of Asf1 by RNA interference impedes DNA unwinding at replication sites, and similar defects
arise from overproduction of new histone H3-H4 that compromises Asf1 function. These data link Asf1 chaperone function, histone
supply, and replicative unwinding of DNA in chromatin. We propose that Asf1, as a histone acceptor and donor, handles parental
and new histones at the replication fork via an Asf1–(H3-H4)–MCM2–7 intermediate and thus provides a means to fine-tune replication
fork progression and histone supply and demand.

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Available from: Adam James L Cook, Oct 05, 2015
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    • "ASF1 binds a heterodimeric histone H3-H4 complex through its conserved N-terminal domain (aa 1–155) and impedes the formation of the (H3-H4) 2 tetramer both inside the nucleus and in the cytoplasm (English et al., 2005). Humans have two ASF1 paralogs, ASF1a and ASF1b, both of which can be co-purified with the MCM 2-7 replicative helicase and histones H3 and H4 from HeLa cell nuclear extract, while only the MCM2 subunit can be pulled down by ASF1a or ASF1b together with H3 and H4 when using cytosolic extract of the same cells (Groth et al., 2007). In vitro studies showed that an N-terminal of human MCM2 (aa 63–154) binds histone H3 directly through a conserved motif (Foltman et al., 2013; Ishimi et al., 1998). "
    Protein & Cell 07/2015; 6(9). DOI:10.1007/s13238-015-0190-0 · 3.25 Impact Factor
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    • "This distribution pattern is similar to endogenous RPA as shown by immunofluorescence (Fig. 1B). Sub-nuclear structures with higher local concentrations were independent of the cell cycle phase and were previously described to co-localize with promyelocytic leukemia (PML) body markers [33] [34]. "
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    ABSTRACT: The ability of replication protein A (RPA) to bind single-stranded DNA (ssDNA) underlines its crucial roles during DNA replication and repair. A combination of immunofluorescence and live cell imaging of GFP-tagged RPA70 revealed that RPA, in contrast to other replication factors, does not cluster into replication foci, which is explained by its short residence time at ssDNA. In addition to replication, RPA also plays a crucial role in both the pre- and post-incision steps of nucleotide excision repair (NER). Pre-incision factors like XPC and TFIIH accumulate rapidly at locally induced UV-damage and remain visible up to 4 h. However, RPA did not reach its maximum accumulation level until 3 h after DNA damage infliction and a chromatin-bound pool remained detectable up to 8 h, probably reflecting its role during the post-incision step of NER. During the pre-incision steps of NER, RPA could only be visualized at DNA lesions in incision deficient XP-F cells, however without a substantial increase in residence time at DNA damage. Together our data show that RPA is an intrinsically highly dynamic ssDNA-binding complex during both replication and distinct steps of NER.
    DNA Repair 12/2014; 24. DOI:10.1016/j.dnarep.2014.09.013 · 3.11 Impact Factor
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    • "Anti-Silencing Function 1 (Asf1) is a highly conserved histone chaperone, which assists essentially all aspects of chromatin biology, including genome silencing by evicting/depositing H3/H4 dimers [8]. It participates in regulating histone synthesis [9], maintains supply of histones, interacts with DNA replication machinery at active replication forks, helps progression of replication fork and maintains replisome integrity [10]–[12]. It cooperates with other chaperones like CAF1, HIR, FACT and several other histone-binding factors in replication-coupled or replication-independent chromatin assembly [13]–[16]. "
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    ABSTRACT: Genome-wide participation and importance of the histone chaperone Asf1 (Anti-Silencing Function 1) in diverse DNA transactions like replication, repair, heterochromatic silencing and transcription are well documented. Yet its genome-wide targets have not been reported. Using ChIP-seq method, we found that yeast Asf1 associates with 590 unique targets including centromeres, telomeres and condensin-binding sites. It is found selectively on highly transcribed regions, which include replication fork pause sites. Asf1 preferentially associates with the genes transcribed by RNA polymerase (pol) III where its presence affects RNA production and replication-independent histone exchange. On pol II-transcribed genes, a negative correlation is found between Asf1 and nucleosome occupancy. It is not enriched on most of the reported sites of histone exchange or on the genes, which are misregulated in the asf1Δ cells. Interestingly, chromosome-wide distributions of Asf1 and one of the condensin subunits, Brn1 show a nearly identical pattern. Moreover, Brn1 shows reduced occupancy at various condensin-binding sites in asf1Δ cells. These results along with high association of Asf1 with heterochromatic centromeres and telomeres ascribe novel roles to Asf1 in condensin loading and chromatin dynamics.
    PLoS ONE 09/2014; 9(9):e108652. DOI:10.1371/journal.pone.0108652 · 3.23 Impact Factor
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