Hbo1 Links p53-Dependent Stress Signaling to DNA Replication Licensing

Department of Microbiology, University of Virginia Health System, P.O. Box 800734, Charlottesville, VA 22908-0734, USA.
Molecular and Cellular Biology (Impact Factor: 4.78). 02/2008; 28(1):140-53. DOI: 10.1128/MCB.00662-07
Source: PubMed


Hbo1 is a histone acetyltransferase (HAT) that is required for global histone H4 acetylation, steroid-dependent transcription,
and chromatin loading of MCM2-7 during DNA replication licensing. It is the catalytic subunit of protein complexes that include
ING and JADE proteins, growth regulatory factors and candidate tumor suppressors. These complexes are thought to act via tumor
suppressor p53, but the molecular mechanisms and links between stress signaling and chromatin, are currently unknown. Here,
we show that p53 physically interacts with Hbo1 and negatively regulates its HAT activity in vitro and in cells. Two physiological
stresses that stabilize p53, hyperosmotic shock and DNA replication fork arrest, also inhibit Hbo1 HAT activity in a p53-dependent
manner. Hyperosmotic stress during G1 phase specifically inhibits the loading of the MCM2-7 complex, providing an example of the chromatin output of this pathway.
These results reveal a direct regulatory connection between p53-responsive stress signaling and Hbo1-dependent chromatin pathways.

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Available from: C. David Allis, Mar 25, 2015
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    • "Plasmid pBS GAL4DBD-E2F1 was a generous gift from Dr Erik Flemington (49). Other cDNAs were generous gifts of Dr Masayoshi Iizuka [HBO1, HBO1G485A (50)], Dr Anindya Dutta [Orc2 (26)], Dr Iwao Kukimoto [Cdc45 (51)] and Dr Hideo Nishitani [Cdt1 (52)]. These cDNAs, as well as Mcm7 and DUE-B cDNAs (cloned from a human cDNA library) were fused to the GAL4 DNA binding domain (GAL4DBD, amino acids 1–147), and replaced the EGFP cDNA in pEGFP N1 (Clontech), except that GAL4DBD-Cdt1 was expressed in pcDNA3.1 (Invitrogen). "
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    ABSTRACT: The specification of mammalian chromosomal replication origins is incompletely understood. To analyze the assembly and activation of prereplicative complexes (pre-RCs), we tested the effects of tethered binding of chromatin acetyltransferases and replication proteins on chromosomal c-myc origin deletion mutants containing a GAL4-binding cassette. GAL4DBD (DNA binding domain) fusions with Orc2, Cdt1, E2F1 or HBO1 coordinated the recruitment of the Mcm7 helicase subunit, the DNA unwinding element (DUE)-binding protein DUE-B and the minichromosome maintenance (MCM) helicase activator Cdc45 to the replicator, and restored origin activity. In contrast, replication protein binding and origin activity were not stimulated by fusion protein binding in the absence of flanking c-myc DNA. Substitution of the GAL4-binding site for the c-myc replicator DUE allowed Orc2 and Mcm7 binding, but eliminated origin activity, indicating that the DUE is essential for pre-RC activation. Additionally, tethering of DUE-B was not sufficient to recruit Cdc45 or activate pre-RCs formed in the absence of a DUE. These results show directly in a chromosomal background that chromatin acetylation, Orc2 or Cdt1 suffice to recruit all downstream replication initiation activities to a prospective origin, and that chromosomal origin activity requires singular DNA sequences.
    Full-text · Article · May 2013 · Nucleic Acids Research
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    • "Hbo1 also associates with the tumor suppressor, p53, and this association negatively regulates Hbo1 enzymatic activity. Cellular stress agents other than DNA damage, such as hyperosmotic stress, activate p53 (Vogelstein et al., 2000), and this activation was suggested to inhibit the HAT activity of Hbo1 and consequently, origin licensing (Iizuka et al., 2008). Hbo1 can also acetylate multiple pre-RC components in vitro however, so its role in pre-RC assembly may also be through direct modification of licensing proteins (Iizuka et al., 2006). "

    Full-text · Chapter · Sep 2011
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    • "Several recent studies in human cells have demonstrated that the HAT HBO1 is involved in the loading of MCM proteins on chromatin in early G1 phase [10], [11], [12] and in the progression of replication forks in S-phase [13]. Furthermore, HBO1 seems to respond to p53 and FAD24 to halt cell cycle progression [14], [15]. HBO1 has no obvious structural homologue in S.cerevisiae, however the Sas2p-containing HAT complex NuA3 has been proposed as a remote functional homologue [16], [17]. "
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    ABSTRACT: GCN5 encodes one of the non-essential Histone Acetyl Transferases in Saccharomyces cerevisiae. Extensive evidence has indicated that GCN5 is a key regulator of gene expression and could also be involved in transcriptional elongation, DNA repair and centromere maintenance. Here we show that the deletion of GCN5 decreases the stability of mini-chromosomes; that the tethering of Gcn5p to a crippled origin of replication stimulates its activity; that high dosage of GCN5 suppresses conditional phenotypes caused by mutant alleles of bona fide replication factors, orc2-1, orc5-1 and mcm5-461. Furthermore, Gcn5p physically associates with origins of DNA replication, while its deletion leads to localized condensation of chromatin at origins. Finally, Deltagcn5 cells display a deficiency in the assembly of pre-replicative complexes. We propose that GCN5 acts as a positive regulator of DNA replication by counteracting the inhibitory effect of Histone Deacetylases.
    Full-text · Article · Jan 2010 · PLoS ONE
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