Department of MedicineMassachusetts General Hospital Cancer Center
Building 149 13th Street 7-213
Charlestown, MA 02129
Visit my lab page here.
The Whetstine laboratory is interested in understanding how the chromatin microenvironment regulates gene expression while maintaining a stable genome. Our ultimate goal is to harness this mechanistic understanding to identify novel therapeutic opportunities and to block chemotherapeutic resistance. We integrate biochemistry, genetics, genomics and computation to elucidate chromatin modulators involved in these processes. We have initiated these types of studies by focusing on a specific class of chromatin regulators, the JmjC-containing histone demethylases. Since the discovery of these chromatin regulators, my laboratory has started screening tumors for genomic anomalies (copy changes and mutations) in this class of enzyme and examining their molecular roles at a biochemical, molecular and in vivo level. These combined approaches will determine whether tumors with alterations in JmjC enzymes provide an opportunity to modify conventional chemotherapy and identify novel molecular diagnostics. Lab website: www.whetstinelab.com
Epigenetic Mechanisms Modulating Cancer Drug Response
Events within the nucleus are governed by a number of processes, but increasing information emphasizes the relationship between post-translational modifications (PTMs) on the histones within the chromatin and proper developmental patterning and pathologies like cancer. The N-terminal tails of histones are subject to a plethora of PTMs including phosphorylation, ubiquitination, acetylation and methylation. Each modification can affect chromatin architecture, but the sum of these modifications may be the ultimate determinant of the chromatin state and biological outcome. Research has shown that multiple lysine (K) residues on the tails of histone H3 and H4 are sites for methylation. The site and degree of methylation (mono-, di-, or tri-) are linked to transcriptional activation and repression, cell cycle progression, and DNA damage response. Many biological processes like heterochromatin formation and X-inactivation are regulated by histone methylation; therefore, aberrant methylation can result in human diseases such as cancer. For this reason, organisms have developed enzymes that are responsible for both adding and removing the methyl mark. Our group studies the impact that histone-modifying proteins have on development, behavior and cancer pathology.
My laboratory is focused on understanding the mechanistic impact that methylation dynamics has in human cell culture and model systems (e.g., C. elegans and zebrafish). In particular, we are investigating the impact that the histone 3 lysine 9/36 tri-demethylases have on differentiation, neural behavior and tumorigenesis by understanding their roles in transcriptional and post transcriptional regulation of the coding and noncoding regions of the genome, in cell cycle progression through regulating chromatin structure, and in the stability of the genome. We are also interrogating the mechanisms associated with regulating histone demethylase function. For example, we have demonstrated that KDM4A is modulated throughout the cell cycle by the SCF E3 ubiquitin ligase complex, which is an important regulator of demethylase levels and function during the cell cycle and hypoxia. We have demonstrated that JMJD2A/KDM4A is amplified in a number of tumors, correlates with poor outcome in ovarian cancer patients and regulates the site-specific copy gain of regions implicated in chemotherapy resistance. Through the use of proteomics and genomics, we have been able to identify important associated proteins regulating these KDM4A driven events at regions being directly modulated. Furthermore, we have identified physiological signals that promote KDM4A stabilization and site-specific copy gain of drug resistant regions in the genome from fish to man. Therefore, we are investigating the impact that other cellular input signals have on copy number through the modulation of chromatin regulators.
The laboratory will interrogate the functional role of histone demethylases by using genomic (ChIP-seq, microarrays, and RNA-seq), proteomic (MS-MS complexes and PTMs), cytological (live imaging and deconvolution confocal microscopy) and genetic (C. elegans, human cell lines, and zebrafish) approaches. Using these strategies, we have uncovered roles for the C. elegans JMJD-2 enzyme in genomic stability and DNA replication. We have extended these studies to demonstrate a conserved role for human JMJD2A/KDM4A in DNA replication and demonstrated that ubiquitin plays a key role in this regulation. Furthermore, we uncovered a conserved role for chromatin states and KDM4A in modulating rereplication at specific sites in the genome. The rereplication promotes site-specific copy gains of drug resistant regions. This series of discoveries identified the first enzyme, physiological condition and chromatin states that modulate copy gain and selection of drug resistant regions across cancer types. Therefore, combining model systems with human cell culture models as well as integrating multiple approaches, we are poised to uncovered mechanisms impacting genome stability and drug resistant gene selection across tumors.
Last Update: 8/6/2015