MSK activity and H3 phosphorylation mediate chromatin remodeling required for expression of immediate-early genes
| dc.contributor.author | Drobic, Bojan | |
| dc.contributor.examiningcommittee | Eisenstat, David (Human Anatomy and Cell Science) Gibson, Spencer (Biochemsitry and Medical Genetics) Wilkins, John (Biochemsitry and Medical Genetics) Cheung, Peter (Ontario Cancer Institute) | en |
| dc.contributor.supervisor | Davie, James R. (Biochemsitry and Medical Genetics) | en |
| dc.date.accessioned | 2010-04-09T15:31:02Z | |
| dc.date.available | 2010-04-09T15:31:02Z | |
| dc.date.issued | 2010-04-09T15:31:02Z | |
| dc.degree.discipline | Biochemistry and Medical Genetics | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | Normal cellular behaviour in multicellular organisms is achieved by tight control of signaling pathway networks. The mitogen-activated protein kinase (MAPK) signaling cascade is one of these signaling networks, that when deregulated can lead to cellular transformation. Activation of the RAS-RAF-MEK-MAPK (ERK) signal transduction pathway or the SAPK2/p38 pathway results in the activation of mitogen- and stress-activated protein kinases 1 and 2 (MSK1/2). Subsequently, MSKs go on to phosphorylate histone H3 at Ser10 and Ser28.Here, we demonstrate that the activities of ERK and MSK1, but not p38, are elevated in Hras-transformed cells (Ciras-3) relative to these activities in the parental 10T1⁄2 cells. Analyses of the subcellular distribution of MSK1 showed that the H3 kinase was similarly distributed in Ciras-3 and 10T1/2 cells, with most MSK1 being present in the nucleus. In contrast to many other chromatin modifying enzymes, MSK1 was loosely bound in the nucleus and was not a component of the nuclear matrix. Our results provide evidence that oncogene-mediated activation of the RAS-MAPK signal transduction pathway elevates the activity of MSK1, resulting in the increased steady-state levels of phosphorylated H3, which may contribute to the chromatin decondensation and aberrant gene expression observed in oncogene-transformed cells. Furthermore, upon activation of the ERK and p38 MAPK pathways, the MSK1/2- mediated nucleosomal response, including H3 phosphorylation at serine 28 or 10, is coupled with the induction of immediate-early gene transcription. The outcome of this response, varying with the stimuli and cellular contexts, ranges from neoplastic transformation to neuronal synaptic plasticity. Here, we used sequential co-immunoprecipitation assays and chromatin immunoprecipitation (ChIP) assays on mouse fibroblast 10T1/2, Ciras-3 and MSK1 knockdown 10T1/2 cells to show that H3 serine 28 and 10 phosphorylation leads to promoter remodeling. MSK1, in complexes with phospho-serine adaptor 14-3-3 proteins and BRG1 (the ATPase subunit of the SWI/SNF remodeler) is recruited to the promoter of target genes by transcription factors such as ELK-1 or NFκB. Following MSK1-mediated H3 phosphorylation, BRG1 associates with the promoter of target genes via 14-3-3 proteins, which act as scaffolds. The recruited SWI/SNF remodels nucleosomes at the promoter of immediate-early genes enabling the binding of transcription factors like JUN and the onset of transcription. Since RAS-MAPK activated MSKs mediate H3 phosphorylation that is required for expression of various immediate-early gene products involved in cellular transformation, inhibition of MSK activity may be a therapeutic target that could be exploited in cancers with upregulated RAS-MAPK signaling. | en |
| dc.description.note | May 2010 | en |
| dc.format.extent | 3310524 bytes | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.citation | Drobic Bojan, Perez-Cadahia Beatriz, Jenny Yu, Sam Kam-Pun Kung and Davie James R (2010). Promoter chromatin remodeling of immediate-early genes is mediated through H3 phosphorylation at either serine 28 or 10 by the MSK1 multi-protein complex. Nucleic Acids Res. [Epub ahead of print]. | en |
| dc.identifier.citation | Perez-Cadahia Beatriz, Drobic Bojan and Davie James R (2009). H3 phosphorylation: dual role in mitosis and interphase. Biochem. Cell Biol. 87(5):695-709. | en |
| dc.identifier.uri | http://hdl.handle.net/1993/3953 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | Signaling | en |
| dc.subject | RAS-MAPK | en |
| dc.subject | Chromatin | en |
| dc.subject | H3 phosphorylation | en |
| dc.subject | Gene expression | en |
| dc.title | MSK activity and H3 phosphorylation mediate chromatin remodeling required for expression of immediate-early genes | en |
| dc.type | doctoral thesis | en_US |