Probing the reaction coordinate of the p300/CBP histone acetyltransferase with bisubstrate analogs

Department of Pharmacology and Molecular Sciences, Johns Hopkins Medical Institute, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
Bioorganic Chemistry (Impact Factor: 2.15). 02/2011; 39(1):42-7. DOI: 10.1016/j.bioorg.2010.10.004
Source: PubMed


Histone and protein acetylation catalyzed by p300/CBP transcriptional coactivator regulates a variety of key biological pathways. This study investigates the proposed Theorell-Chance or "hit-and-run" catalytic mechanism of p300/CBP histone acetyltransferase (HAT) using bisubstrate analogs. A range of histone peptide tail peptide-CoA conjugates with different length linkers were synthesized and evaluated as inhibitors of p300 HAT. We show that longer linkers between the histone tail peptide and the CoA substrate moieties appear to allow for dual engagement of the two binding surfaces. Results with D1625R/D1628R double mutant p300 HAT further confirm the requirement for a negatively charged surface on the enzyme to interact with the histone tail.

Full-text preview

Available from:
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We previously identified novel thiazole derivatives able to reduce histone acetylation and histone acetyltransferase (HAT) activity in yeast. Among these compounds, 3-methylcyclopentylidene-[4-(4'-chlorophenyl)thiazol-2-yl]hydrazone (CPTH6) has been selected and used throughout this study. The effect of CPTH6 on histone acetylation, cell viability and differentiation, cell-cycle distribution, and apoptosis in a panel of acute myeloid leukemia and solid tumor cell lines has been evaluated. Here, we showed that CPTH6 leads to an inhibition of Gcn5 and pCAF HAT activity. Moreover, it inhibits H3/H4 histones and α-tubulin acetylation of a panel of leukemia cell lines. Concentration- and time-dependent inhibition of cell viability, paralleled by accumulation of cells in the G(0)/G(1) phase and depletion from the S/G(2)M phases, was observed. The role of mitochondrial pathway on CPTH6-induced apoptosis was shown, being a decrease of mitochondrial membrane potential and the release of cytochrome c, from mitochondria to cytosol, induced by CPTH6. Also the involvement of Bcl-2 and Bcl-xL on CPTH6-induced apoptosis was found after overexpression of the two proteins in leukemia cells. Solid tumor cell lines from several origins were shown to be differently sensitive to CPTH6 treatment in terms of cell viability, and a correlation between the inhibitory efficacy on H3/H4 histones acetylation and cytotoxicity was found. Differentiating effect on leukemia and neuroblastoma cell lines was also induced by CPTH6. These results make CPTH6 a suitable tool for discovery of molecular targets of HAT and, potentially, for the development of new anticancer therapies, which warrants further investigations.
    Full-text · Article · Nov 2011 · Clinical Cancer Research
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel strategy to prepare bisubstrate based inhibitors for histone acetyltransferases is presented. To obtain these, azido peptides derived from histone H3 incorporating either a serine or a phosphoserine residue were connected to a propargyl coenzyme A derivative through copper catalyzed click chemistry. The resulting inhibitors were tested with therapeutically relevant acetyltransferase PCAF. Increased potency of the phosphoserine containing inhibitor was observed. The synthetic strategy presented may be used for developing bisubstrate based inhibitors against any acetyltransferase.
    No preview · Article · Dec 2013 · Bioorganic & medicinal chemistry letters
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The transcriptional coactivator and histone acetyltransferase (HAT) p300 acetylates the four core histones and other transcription factors to regulate a plethora of fundamental biological processes including cell growth, development, oncogenesis and apoptosis. Recent structural and biochemical studies on the p300 HAT domain revealed a Theorell-Chance, or "hit-and-run", catalytic mechanism. Nonetheless, the chemical mechanism of the entire reaction process including the proton transfer (PT) scheme and consequent acetylation reaction route still remains unclear. In this study, a combined computational strategy consisting of molecular modeling, molecular dynamic (MD) simulation and quantum mechanics/molecular mechanics (QM/MM) simulation was applied to elucidate these important issues. An initial p300/H3/Ac-CoA complex structure was modeled and optimized using a 100 ns MD simulation. Residues that play important roles in substrate binding and the acetylation reaction were comprehensively investigated. For the first time, these studies reveal a plausible PT scheme consisting of Y1394, D1507 and a conserved crystallographic water molecule, with all components of the scheme being stable during the MD simulation and the energy barrier low for proton transfer to occur. The two-dimensional potential energy surface for the nucleophilic attack process was also calculated. The comparison of potential energies for two possible elimination half-reaction mechanisms revealed that Y1467 reprotonates the coenzyme-A leaving group to form product. This study provides new insights into the detailed catalytic mechanism of p300 and has important implications for the discovery of novel small molecule regulators for p300.
    Full-text · Article · Feb 2014 · The Journal of Physical Chemistry B
Show more