The human genome encodes approximately 25,000 proteins. Considering that about 60% of genes are alternatively processed for an average of 2-4 messages per gene, and that greater than 200 post-translational modifications are known, then the protein diversity available to organize a complex organism is vast. Yet we know the function of only a minority of those proteins. A key issue for biology is whether this high protein diversity reflects functional diversity, or is a means to increase evolutionary adaptation. To that end the broader goal of our laboratory is to discover functions for the portion of the human genome that is poorly annotated. Our immediate goal is develop large scale programs that couple genomics and proteomics to understand the causes, and identify therapeutic targets, for multi-factorial diseases such as cancer.
In general, the functions of most proteins are defined or mediated through interactions with other proteins. Within a cell these interactions are organized into a complex network regulated, in part, through phosphorylation by an elaborate interconnected system of kinases and phosphatases. We are developing systems to study protein-protein interactions and post-translational modifications, theorizing that the functions of proteins and their isoforms are reflected in their protein partners and phosphorylation states.
Protein-protein interaction mapping in cancer cells
We investigate the functional mechanisms of proteins implicated in cancer. We express epitope-tagged versions of the proteins in tissue culture cells and determine the identity of proteins in the immunoprecipitations using nano-flow reverse phase liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-MS/MS). From this information we build protein-protein interaction maps with the goal of confirming our hypotheses through molecular intervention in the function of key proteins. The goal is to identify new targets for therapeutic intervention.
Our current project focuses on the protein interaction partners of a serine/threonine protein kinase. Our protein-protein interaction mapping data supports previous hypotheses that the kinase coordinately regulates alternative splicing and transcription. We are studying its function in regulating steps in splicing and transcription at the biochemical and biological level, and the role of its kinase activity in regulating the function of its interaction partners. The kinase itself is phosphorylated and phosphorylation of some its sites are attenuated by tyrosine kinase inhibitors used for cancer treatment. This suggests the kinase resides in important signaling cascades affecting cell proliferation. We are investigating how phosphorylation of the kinase regulates its downstream functions.
Protein isoform function
We generally do not know the functional differences amongst the isoforms of the same protein. In this project we are studying the isoforms of our protein kinase model system. The protein possesses multiple protein-protein interaction domains and phosphorylation sites. Using mass-spectrometry-based methods we hope to elucidate the protein partners of the isoforms of the kinase and their phosphorylation states. This will inform us of the functional differences amongst the isoforms and how they may differentially regulate their molecular substrates. With this initial model system we hope to develop proteomic strategies to assess protein isoform functions at a relatively large multiplexed scale and broadly apply the strategies to explore the functions of protein isoforms in cell regulation and disease.
Highlights of Past Research
Before joining the GSC Dr. Morin spent several years in the biotechnology industry. As VP Biology at MDS Proteomics in Toronto, Ontario, he led efforts to identify new therapeutic targets employing large scale protein interaction mapping and mass spectrometry. As Director of Molecular Biology and Biochemistry with Geron Corporation in Menlo Park California, Dr. Morin oversaw projects and programs focusing on telomerase biochemistry and drug discovery, vector biology, and functional genomics for cancer therapeutics. These programs at Geron were the first to clone the human telomerase catalytic subunit. We were also the first to reconstitute the RNA and protein subunits of telomerase in vitro, which allowed the determination of the critical residues and their functions in the protein subunit of the human enzyme. We cloned and characterized the basic regulatory elements of the hTERT promoter and established a minimal promoter that maintains tumor-restricted expression. We also developed vectors used to restore hTERT expression and telomerase activity in primary human cells, this milestone event demonstrated that hTERT could immortalize human cells but maintain their normal function.
As an assistant professor at the University of California, Davis and as a postdoctoral fellow at Yale University, Dr. Morin explored the structure and functions of human telomerase, and was the first to observe human telomerase activity. The work showed that telomerase can recognize non-telomeric primers and defined the recognition rules for primer binding. These results enabled high-throughput in vitro telomerase activity assays at pharmaceutical companies worldwide for the discovery of small molecule inhibitors of telomerase for cancer therapy.
"Cytosolic protein interactions of the schizophrenia susceptibility gene dysbindin." Mead C-LR, Kuzyk MA, Moradian A, Wilson GM, Holt RA and Morin GB. J. Neurochemistry. 2010 Jun;113(6):1491-503. [Epub 2010 Mar 14].
"ALEXA – A microarray design platform for alternative expression analysis." Griffith M. Tang MJ, Griffith OL, Chan SY, Asano JK, Zeng T, Flibotte S, Ally A, Baross A, Morin RD, Hirst M, Jones SJM, Morin GB, Tai IT, and Marra M. Nature Methods. 2008 Feb;5(2):118.
"Large-scale mapping of human protein-protein interactions by mass spectrometry." Ewing RM, Chu P, Elisma F, Li H, Taylor P, Climie S, McBroom-Cerajewski L, Robinson MD, O'Connor L, Li M, Taylor R, Dharsee M, Ho Y, Heilbut A, Moore L, Zhang S, Ornatsky O, Bukhman YV, Ethier M, Sheng Y, Vasilescu J, Abu-Farha M, Lambert JP, Duewel HS, Stewart II, Kuehl B, Hogue K, Colwill K, Gladwish K, Muskat B, Kinach R, Adams SL, Moran MF, Morin GB, Topaloglou T, Figeys D. Mol Syst Biol. 2007;3:89. [Epub 2007 Mar 13].
"Modification of the Creator Recombination System for Proteomics Applications - Improved Expression by Addition of Splice Sites." Colwill K, Wells CD, Elder K, Goudreault M, Hersi K, Kulkarni S, Hardy WR, Pawson T, and Morin GB. BMC Biotech. 2006 Mar 6;6:13.
"Effect of TERT over-expression on the long-term transplantation capacity of hematopoietic stem cells." Allsopp RC, Morin GB, Horner JW, DePinho RA, Harley CB, Weissman IL. Nature Medicine. 2003 Apr;9(4):369-71.
"TANK2, a new TRF1-associated poly(ADP-ribose) polymerase, causes rapid induction of cell death upon overexpression." Kaminker PG, Kim SH, Taylor RD, Zebarjadian Y, Funk WD, Morin GB, Yaswen P, Campisi J. J Biol Chem. 2001 Sep 21;276(38):35891-9. [Epub 2001 Jul 13].
"Expression of Mouse Telomerase Reverse Transcriptase during Development, Differentiation, and Proliferation." Greenberg RA, Allsopp RC, Chin L, Morin GB, DePinho RA. Oncogene. 1998 Apr 2;16(13):1723-30.
"Extension of safe-Span by Introduction of Telomerase into Normal Human Cells." Bodnar AG, Ouellette M, Frolkis M, Holt SE, Chiu CP, Morin GB, Harley CB, Shay, SW, Lichtsteiner L,Wright WE. Science. 1998 Jan 16;279(5349):349-52.
"Reconstitution of Human Telomerase with the Template RNA Component hTR and the Catalytic Protein Subunit hTRT." Weinrich SL, Pruzan R, Ma L, Ouellette M, Tesmer V M, Holt SE, Bodnar AG, Lichtsteiner S, Kim NW, Trager JB, Taylor RD, Carlos R, Andrews WH, Wright WE, Shay JW, Harley CB, Morin GB. Nature Genetics. 1997 Dec;17(4):498-502.
"Telomerase Catalytic Subunit Homologs from Fission Yeast and Human." Nakamura TM, Morin GB, Chapman KB, Weinrich SL, Andrews WH, Lingner J, Harley CB, Cech TR. Science. 1997 Aug 15;277(5328):955-9.
"Recognition of a Chromosome Truncation Site Associated with α-Thalassaemia by Human Telomerase." Morin GB. Nature. 1991 Oct 3;353(6343):454-6.
"The Human Telomere Terminal Transferase is a Ribonucleoprotein that Synthesizes TTAGGG Repeats." Morin, GB. Cell. 1989 Nov 3;59(3):521-9.
Gregg Morin's Complete Publications List including selected links to full text articles.