The laboratory works primarily on understanding how mammalian cells detect and repair DNA double-strand breaks. This ability of cells to correctly repair DNA damage is critical for maintaining genomic integrity and for preventing the loss of genomic information. Tumor cells frequently acquire mutations in DNA repair proteins (e.g. brca1/brca2/p53), leading to increased genomic instability and progression of tumors. Further, altered regulation of DNA repair pathways can lead to tumor resistance to both chemotherapy and radiation therapy. By identifying the proteins which maintain DNA integrity, and determining how these are altered in human tumors, we aim to identify new protein targets for development of anti-cancer agents.
Overview: Our current research is focused on understanding how chromatin structure and chromatin organization impact DNA repair. Chromatin is a dynamic structure containing both open, transcriptionally active regions (euchromatin) and compacted, transcriptionally inactive regions (heterochromatin). DNA damage within these distinct chromatin domains requires specific sets of remodeling factors to alter chromatin structure and allow access of the DNA repair machinery to the site of DNA damage. We are currently examining the role of histone modifications, and in particular histone methylation, in regulating the ability of cells to detect and repair DNA damage within distinct chromatin domains. This work utilizes Zinc Finger and CRISPR-targeted nucleases to create DNA breaks in defined chromatin domains. Combining these with ChIP and ChIP-seq approaches allows us to determine how DNA damage alters local chromatin organization and epigenetics, and to determine how chromatin organization influences the efficiency of DNA repair in diverse chromatin domains.
ATM and Tip60: The ATM kinase is the master regulator of the cells response to DNA double strand breaks. Our results indicate that a specific histone modification, H3K9me3, plays a critical role in the DNA damage response. H3K9 methylation is increased after DNA damage and drives activation of the Tip60 acetyltransferase. Tip60 then acetylates and activates the ATM kinase. Signals generated on the chromatin at sites of DNA damage are therefore critical for regulating DNA damage responses.
NuA4 and Tip60: Tip60 is also a key component of NuA4, a remodeling complex which is rapidly recruited to damaged chromatin. NuA4 has 2 critical catalytic activities: the p400 remodeling ATPase, which rapidly exchanges the histone variant H2A.Z onto the chromatin, and Tip60, which acetylates histone H4. The combination of H2A.Z exchange and H4 acetylation decreases nucleosome stability adjacent to DNA breaks, facilitating access of the DNA repair machinery and processing of the damaged DNA template. This relaxation of the chromatin structure by NuA4 also promotes the recruitment of DNA repair proteins such as brca1 and 53BP1 to sites of damage. The NuA4 complex therefore plays a central role in reorganizing the chromatin template at DSBs to create an efficient substrate for the DNA repair machinery to act on.
Histone H2A.Z and cancer: H2A.Z is highly expressed in many tumors, including breast, lung and glioma. Overexpression of histone H2A.Z contributes to both altered transcriptional profiles and a decrease in sensitivity of tumors to chemotherapy and radiotherapy. Dissecting the pathways by which H2A.Z can alter transcription and DNA repair will provide new insight into how chromatin organization impacts cancer therapy and etiology. Current work is focused on determining how H2A.Z overexpression in gliomas contributes to the poor prognosis and lack of therapeutic response of these tumors.
As part of the Chromatin Therapeutics Discovery Group (CTDG) we carry out small molecule inhibitor screening of key chromatin regulatory proteins (including lysine methyltransferases and acetyltransferases) which are deregulated in tumor cells. We aim to identify novel epigenetic therapies which can be used to reset the altered epigenetic signatures found in tumor cells. By resetting these epigenetic switches, we aim to erase the altered chromatin states which drive the transformed phenotype and improve therapeutic outcome for cancer.
Overview: Our current research is focused on understanding how chromatin structure and chromatin organization impact DNA repair. Chromatin is a dynamic structure containing both open, transcriptionally active regions (euchromatin) and compacted, transcriptionally inactive regions (heterochromatin). DNA damage within these distinct chromatin domains requires specific sets of remodeling factors to alter chromatin structure and allow access of the DNA repair machinery to the site of DNA damage. We are currently examining the role of histone modifications, and in particular histone methylation, in regulating the ability of cells to detect and repair DNA damage within distinct chromatin domains. This work utilizes Zinc Finger and CRISPR-targeted nucleases to create DNA breaks in defined chromatin domains. Combining these with ChIP and ChIP-seq approaches allows us to determine how DNA damage alters local chromatin organization and epigenetics, and to determine how chromatin organization influences the efficiency of DNA repair in diverse chromatin domains.
ATM and Tip60: The ATM kinase is the master regulator of the cells response to DNA double strand breaks. Our results indicate that a specific histone modification, H3K9me3, plays a critical role in the DNA damage response. H3K9 methylation is increased after DNA damage and drives activation of the Tip60 acetyltransferase. Tip60 then acetylates and activates the ATM kinase. Signals generated on the chromatin at sites of DNA damage are therefore critical for regulating DNA damage responses.
NuA4 and Tip60: Tip60 is also a key component of NuA4, a remodeling complex which is rapidly recruited to damaged chromatin. NuA4 has 2 critical catalytic activities: the p400 remodeling ATPase, which rapidly exchanges the histone variant H2A.Z onto the chromatin, and Tip60, which acetylates histone H4. The combination of H2A.Z exchange and H4 acetylation decreases nucleosome stability adjacent to DNA breaks, facilitating access of the DNA repair machinery and processing of the damaged DNA template. This relaxation of the chromatin structure by NuA4 also promotes the recruitment of DNA repair proteins such as brca1 and 53BP1 to sites of damage. The NuA4 complex therefore plays a central role in reorganizing the chromatin template at DSBs to create an efficient substrate for the DNA repair machinery to act on.
Histone H2A.Z and cancer: H2A.Z is highly expressed in many tumors, including breast, lung and glioma. Overexpression of histone H2A.Z contributes to both altered transcriptional profiles and a decrease in sensitivity of tumors to chemotherapy and radiotherapy. Dissecting the pathways by which H2A.Z can alter transcription and DNA repair will provide new insight into how chromatin organization impacts cancer therapy and etiology. Current work is focused on determining how H2A.Z overexpression in gliomas contributes to the poor prognosis and lack of therapeutic response of these tumors.
As part of the Chromatin Therapeutics Discovery Group (CTDG) we carry out small molecule inhibitor screening of key chromatin regulatory proteins (including lysine methyltransferases and acetyltransferases) which are deregulated in tumor cells. We aim to identify novel epigenetic therapies which can be used to reset the altered epigenetic signatures found in tumor cells. By resetting these epigenetic switches, we aim to erase the altered chromatin states which drive the transformed phenotype and improve therapeutic outcome for cancer.
