Our lab has three main interests: understanding the physiological function of poly(ADP-ribose) and the 17 PARPs that polymerize it, understanding poly(ADP-ribose) function during cell stress and disease, and identifying novel molecules required for cell division.
Poly(ADP-ribose) is a poorly understood biopolymer and post-translational modification required for life in all multicellular organisms. While primarily known for its role in DNA damage repair, it functions in many essential cellular processes such as cell division and cell cycle progression as well as transcriptional and translational regulation. Poly(ADP-ribose) is polymerized onto acceptor proteins by a family of 17 PARPs using NAD+ as substrate. The majority of these are newly identified and uncharacterized. Several are up-regulated in cancers. Mis-regulation of poly(ADP-ribose) is lethal, and appears to be important in human diseases such as cancers, prompting pharma-ceutical companies to develop candidate therapeutics targeting the poly(ADP-ribose) polymerases (PARPs).
What makes poly(ADP-ribose) so interesting is that it acts as both a traditional protein modification, like phosphorylation or ubiquitination, and a macromolecule with chemical similarities to nucleic acids and carbohydrates. Like these other polymers, poly(ADP-ribose) binds specific proteins, however due to its rapid turnover dynamics, protein binding can be regulated in time and space making poly(ADP-ribose) an ideal mediator of dynamic protein localization.
To better understand poly(ADP-ribose) and PARPs, we are taking a systems-level approach by first determining where, when and how poly(ADP-ribose) and PARPs function in the cell. We have started by characterizing the localization and function of each of the 17 PARPs simultaneously using a combination of antibody staining, long-term imaging of GFP fusions, and RNAi. These preliminary experiments have identified several PARPs as essential for somatic cell function and localized the majority of the PARP proteins to the cytoplasm, membranes and vesicles during interphase, and to the mitotic spindle during mitosis. To better understand and identify the biological pathways of PARP function, and to identify functionally conserved mechanisms, we are identifying all PARP binding proteins, and poly(ADP-ribose) acceptor and binding proteins using biochemical approaches. Finally, to understand when PARPs are active, we are designing ways to monitor PARP activity in cells real time using fluorescence microscopy.
Some of the best understood poly(ADP-ribose) functions occur as a response to cell stresses such as DNA damage, and apoptosis. In collaboration with Phil Sharp's lab at MIT, we have identified a poly(ADP-ribose) and PARP requirement in new stress pathways, and have identified specific PARPs that function in these stress responses. Our lab is continuing to identify new stress pathways in which PARPs function, and, with our library of 17 PARP clones and siRNAs, have revisited functions for other PARPs in DNA damage and apoptosis. One long term goal of the lab is to identify mechanistic differences and similarities between physiological and stresss mediated PARP functions. With this information, we hope to determine how PARPs malfunction in human diseases.
Our lab has a long-term interest in cell division, the cytoskeleton and dynamic polymers. To identify new molecules and organelles required for cell division, we developed a method to assemble mitotic spindles in human somatic cell extracts using purified components. Using this technique we hope to identify new molecules and organelles required for spindle function, and identify specific spatio-temporal requirements of protein modifications for spindle function. Finally, this assay will allow us to determine if genotoxic or cytotoxic damage to specific organelles affects spindle function or assembly.
Chang P, Coughlin M, Mitchison TJ. Tankyrase-1 polymerization of poly(ADP-ribose) is required for spindle structure and function. Nature Cell Bio. 2005 Nov; 7(11):1133-9.
Chang P, Jacobson MK, Mitchison TJ. Poly(ADP-ribose) is required for spindle assembly and structure. Nature 2004 Dec 2; 432(7017):645-9.
Louie RK, Bahmanyar S, Siemers KA, Votin V, Chang P, Stearns T, Nelson WJ, Barth AI. Adenomatous polyposis coli and EB1 localize in close proximity of the mother centriole and EB1 is a functional component of centrosomes. Cell Science 2004 Mar 1; 117(Pt 7):1117-28.
Chang P, Giddings TH, Winey M, Stearns T. Epsilon-tubulin is Required for Centriole Duplication and Microtubule Organization. Nature Cell Bio. 2003 Jan; 5(1):71-6.
Chang P, Stearns T. Delta-tubulin and epsilon-tubulin: two new human centrosomal tubulins reveal new aspects of centrosome structure and function. Nature Cell Bio. 2000 Jan; 2(1):30-5.
room E18-270
phone (617) 324-3879
email pchang2@mit.edu
phone (617) 324-3879
Jennifer Cimino
phone (617) 258-6559
email joyoung@mit.edu
