Nuclear Signalling Laboratory
Co-workers: Dr Alison Clayton, Dr Catherine Hazzalin, Dr Duen-Wei Hsu, Mr Nicholas Crump, Mr Ben Lee, Mr Edgar Pogna
We are studying the process by which extracellular stimuli elicit rapid, transient induction of a class of genes called Immediate-Early (IE) genes. These are linked directly by signal transduction cascades to cell surface and intracellular receptors, requiring no new transcription or translation for induction. The process is highly conserved in evolution and is widely deployed within the organism, controlling diverse phenomena such as cell division, differentiation as well as immunological and inflammatory responses.We have characterised IE gene induction in cultured mammalian cells stimulated with physiological (growth factors, cytokines), pharmacological (okadaic acid, phorbol esters and anisomycin) and stress (heat, heavy metal, UV radiation). These agents differentially activate MAP kinase cascades which are targeted to transcription factors controlling IE genes. In addition, MAP kinases activate downstream kinases such as MSKs that phosphorylate nucleosomal proteins histone H3 and HMG-14. The histone H3 tail is also subject to acetylation by transcriptional coactivators that possess intrinsic histone acetyltransferase (HAT) activity, which we showed to be a highly dynamic process targetted to K4 methylated H3 tails.
We recently published high-resolution comparative maps of the distribution and dynamics of several histone H3 modifications across c- fos and c-jun during gene induction. These studies produce a new four-layered model of dynamic histone modifications across genes in mammalian cells.
The first, across the start site and in the coding region, are pre-existing, possibly epigenetic, histone modifications detectable in quiescent G0 cells. The second relates to continuous dynamic turnover of H3acetylation by the action of HATS and HDACs affecting all K4me3- modified H3 in the mouse nucleus. Upon stimulation, a third signalling- dependent set, which includes H3 phosphorylation at IE genes or H4 acetylation at hsp70, appears across the start site. Finally, there are DRB-sensitive modifications restricted to coding regions of these genes, dependent upon passage of Pol II. Thus, four distinct layers contribute to the dynamic appearance and distribution of histone H3 modifications across mammalian genes.
Present research centres (i) on understanding the signalling systems and nucleosomal modifications controlling IE genes, especially quantitative influences observed, (ii) on determining causality and identifying the enzymes involved in dynamic histone modifications, (iii) on addressing evolutionary conservation of these processes using other model systems such as Drosophila and Dictyostelium, and (iv) on developing chromatinised transfection-based model systems in which the complexity of these processes is preserved. As these processes regulate the control of proto-oncogenes and genes encoding pro-inflammatory cytokines such as TNFa, there is considerable current interest in deriving inhibitors in the context of cancer and inflammation.
- Erin M. Bowers, Gai Yan, Chandrani Mukherjee, Andrew Orry, Ling Wang, Marc A. Holbert, Nicholas T. Crump, Catherine A. Hazzalin, Glen Liszczak, Hua Yuan, Cecilia Larocca, S. Adrian Saldanha, Ruben Abagyan, Yan Sun, David J. Meyers, Ronen Marmorstein, Louis C. Mahadevan, Rhoda M. Alani, and Philip A. Cole (2010) Virtual Ligand Screening of the p300/CBP Histone Acetyltransferase: Identification of a Selective Small Molecule Inhibitor, Chemistry and Biology, in press
- Edmunds, J.W., Mahadevan, L.C. and Clayton, A.L. (2008) Dynamic histone H3 methylation during gene induction: HYPB/Setd2 mediates all H3K36 trimethylation. EMBO J., 27, 406-420
- Clayton, A.L, Hazzalin, C.A and Mahadevan, L.C. (2006) Enhanced histone acetylation and transcription: a dynamic perspective. Molecular Cell 23, 289-296
- Macdonald, N., Welburn J. P. I., Noble M. E. M., Nguyen, A., Yaffe, M. B., Clynes, D., Moggs, J. G., Orphanides, G., Thomson, S., Edmunds, J. W., Clayton, A. L., Endicott, J. A., and Mahadevan, L. C. (2005) Molecular basis for the recognition of phosphorylated and phosphoacetylated histone H3 by 14-3-3. Molecular Cell 20, 199-211
- Hazzalin, C. A. and Mahadevan, L. C. (2005) Dynamic acetylation of lysine 4-methylated histone H3 in the mouse nucleus: analysis of c-fos and c-jun. Plos Biology 3, e393
Figure 1: Histone modifications at inducible genes
Figure 2: 45 min subinibitory anisomysin treatment - Mark Dyson et al. J Cell Sci 2005
Figure 3: Molecular Cell journal cover
Figure 4: Immediate-early Gene Induction
Graduate Student and Postdoctoral Positions: Enquiries with CV welcome