Our lab is interested in how the modification of histones affects the organisation of chromatin, and how it helps regulate DNA-templated processes. The human hMOF complex is a useful model to answer these questions. There are at least two histone modifying emzymes in this complex; hMOF and hMSL2.
The human genome comprises an estimated 20-25,000 genes which generate around 200 different cell types. These cells differ greatly in their structure and function yet the genetic material in each is identical. This remarkable diversity is made possible largely through the action of epigenetic mechanisms. These mechanisms act above the level of DNA, precisely controlling gene expression patterns and hence dictating the proper development of an organism. Various epigenetic mechanisms are now recognized and include; modification of the DNA, modifications of histone proteins and incorporation of histone variants.
Our Lab is particularly interested in histone acetylation. This is a reversible modification which is controlled by enzymes: histone acetyl-transferases (HATs), which add acetyl groups to proteins and histone de-acetylases (HDACs), which remove them. Histone acetylation is generally regarded as a transcriptional activating modification. However, it has also been associated with gene repression, DNA repair, DNA replication, and recombination. Considering the involvement of histone acetylation in such fundamental processes, it is not surprising that disruption of the normal acetylation status has been implicated in cancer.
Human MOF complex
hMOF is a HAT that is responsible for the acetylation of histone H4 at lysine 16. In the fruitfly, Drosophila melanogaster, this H4K16ac mediated by dMOF correlates with a two-fold upregulation of transcription required for dosage compensation. The purification of MOF-interacting proteins in both the fruitfly and human cells revealed a number of conserved interacting proteins, suggesting that the function of these complexes is maintained through evolution. More recently, it was found that loss of hMOF and also reduction in H4K16 acetylation levels are frequent occurrences in various human cancers. Thus, studying hMOF and H4K16Ac allows us to investigate the involvement of this particular modification in the development of an important human disease.
Schematic depiction of the potential roles of hMOF in the cell. Acetylation of histone H4 at K16 by hMOF could: (A) facilitate a decrease in either the affinity of histones for DNA or in inter-nucleosomal interactions thus opening up the chromatin structure. (B) act as a binding site for specific proteins that can further modify chromatin, such as transcriptional coactivators or DNA repair proteins. (C) inhibit binding of specific factors such as transcriptional repressive complexes. (D) hMOF could modify a protein(s) important for nuclear stability. This target could be either a nuclear pore or a nuclear membrane associated protein. Following DNA damage: (E) hMOF can activate ATM, one of the cell’s main repair pathways. The mechanism for this activation is unknown but may involve increased acetylation around the sites of damage. (F) the tumor suppressor p53 can be acetylated by hMOF resulting in a decision favouring programmed cell death as opposed to cell cycle arrest. Adapted from Rea, S., Xouri, G., Akhtar, A., (2007) Oncogene 26 (37), 5385-94.
hMOF and gene expression
In Drosophila H4K16 acetylation mediated by dMOF, as part of the MSL complex, was shown to correlate with increased transcription. Depletion of hMOF in human cells has also been shown to affect the expression level of certain genes. However, the exact role of hMOF and H4K16Ac in transcriptional regulation and the mechanism behind this regulation in mammals is not clear. We plan to take in vitro and in vivo approaches to: 1) Determine whether hMOF regulates transcription. 2) Elucidate how hMOF regulates transcription. 3) Explain how hMOF HAT activity is regulated
hMOF in tumour progression
It is now widely accepted that cancer is both a genetic and an epigenetic disease. Perturbations in epigenetic mechanisms such as DNA methylation, histone modifications and chromatin remodeling have been implicated in tumorigenesis. It has recently been shown that both hMOF and H4K16 acetylation levels are frequently reduced in various cancers. However, at the moment, it is unclear whether this loss is a cause or consequence of cell transformation. A second project in the lab will address whether loss of hMOF/H4K16 acetylation plays a functional role in the path to tumorigenesis. We also hope to evaluate the feasibility of hMOF as a biomarker or therapeutic target in various cancers.
hMSL2 in the DNA damage response
hMSL2, a RING-finger domain containing protein, was recently shown to be a ubiquitin ligase that ubiquitylates Histone H2B on lysine 34. This H2BK34ub has been linked to transcriptional regulation. We are hoping to characterise this protein further; to identify other functions and other substrates – if they exist.
- Anna Meller, MSc.
I joined the Rea Lab in 2013. I graduated from the University of West Hungary, Mosonmagyaróvár with an animal breeding degree. Then I studied agricultural biotechnology in Szent István University, Gödöllö and obtained my masters degree. During this period I participated in an exchange studentship and had the chance to study one semester in Hanyang University, Seoul where I first encountered epigenetics and histone modifications.
My PhD project in the lab is to characterise the human MSL2 protein and investigate its involvement in the DNA damage response.
- Karen Lane, MSc.
I originally obtained a Bachelor of Science degree in Pharmacology in 2010. Following this, I obtained a Master’s degree in Biomedical Science from NUI, Galway in 2012. During the course of these studies, my interest and focus shifted more towards cancer research as I completed a project in the NCBES to study the role of tumour necrosis factor (TNF) and it’s interactors in the response of cancer cells to drug treatments, especially in treatment-resistant cancers. This study of more treatment-resistant, aggressive cancers has continued into my PhD project.
Since starting in the lab in January 2014, I have been working to investigate the role of the chromatin modifier hMOF in breast cancer. Loss of hMOF and its subsequent histone acetylation activity has been previously observed in a number of cancers and appears to be linked to a more aggressive cancer phenotype. As I am funded by Breast Cancer Campaign, my goal is to study this further in breast cancer and elucidate whether this loss of hMOF is responsible for the development of a more aggressive cancer phenotype, for example by increasing cell growth, motility or metastasis.
- Lukas Andrzejewski, M.Sc
Since I first learned about Chromatin during my BSc studies at Warsaw University I was intrigued. I therefore started an MSc on the epigenetic topic of chromatin remodelers in the lab of Prof. Andrzej Jerzmanowski. During my MSc I obtained a Summer Fellowship from FEBS (Federation of European Biochemical Societies) and chose Prof. Felice Cervone’s lab at the Sapienza University of Rome. Where I carried out research about receptor like-kinase in A. thaliana involved in defense against pathogens. I joined the Rea lab in August 2012.
My PhD project, funded by the Breast Cancer Campaign, is to investigate how loss of hMOF contributes to cancer, and more specifically, to determine whether hMOF loss contributes to metastasis in Breast Cancer. This may be due to defective epigenetic mechanisms or it may be due to loss of some other key output of hMOF.
- Zheng Lai, M.Sc
I joined Stephen Rea’s lab as a PhD student in September 2009. I graduated with a Bachelor of Science from Sichuan University in China in 2001. Then, I obtained my Masters degree in Institute of Biochemistry and Cell Biology (IBCB), Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences (CAS) in 2006.My MSc program focused on medical genetics.
I finished a mutation screen and analysis of several genes linked with STGD-3 like macular dystrophy in a Chinese pedigree, and the relative results were published in J Cell Mol Med (2005, 9(4): 961-5). Subsequently I started my career in the structural biology laboratory in IBCB, engaging in protein expression and purification with prokaryotic and eukaryotic systems.My research interest is to investigate the functional influence of the human MSL complex on the DNA damage response.
- Simona Moravcovà, M.Sc.
I graduated with a B.Sc. degree in Biology and a M.Sc. degree in Molecular Biology and Genetics of Eukaryotes at the Charles University in Prague, Czech republic. My thesis project, which was done at the Department of Tumor Immunology, Institute of Molecular Genetics, concerned both epigenetic and nonepigenetic regulation of expression of immunoactive molecules on tumor cells.
I am a PhD student and joined the lab in September 2008. My project, funded by IRCSET, involves characterization of the human MSL2 protein and determination of its possible role in ubiquitylation. hMSL2 together with hMOF, is part of the MSL complex which is known to epigenetically regulate gene expression in Drosophila.
- Sandra Clasen, M.Sc.
I joined Dr Rea’s new group in April 2008 as a PhD student. Originally from Germany, I graduated with a Bachelor of Science from both, the FH Bonn-Rhein-Sieg, Germany and the Murdoch University in Perth, Australia in 2006. Immediately after, I started an M.Sc. in Biomolecular Science at the VU Amsterdam. During my Master studies I completed two epigenetics-related research projects in Amsterdam (with Dr. Kooter) and at the MRC Clinical Science Centre in London (with Prof. Festenstein).
My research interest is the epigenetic regulation of gene expression, especially by the modifications of histones. During my PhD I will characterize the functions of the human MOF enzyme in the regulation of gene expression.