Reversible protein phosphorylation and cell proliferation.
Our studies focus on the role of reversible phosphorylation in the regulation of essential steps in cell proliferation. Recently we have focused on the functions and regulation of polo-like kinases (Plk) in mammalian cells. Three mammalian Plks have been identified; Plk1 is expressed during M phase and cytokinesis, whereas Plk2 (Snk) and Plk3 (Fnk) are expressed in other phases of the cell cycle. These enzymes are characterized by their similar N-terminal catalytic domains, as well as a C-terminal domain with highly conserved sequences termed the polo box. We have previously demonstrated that the polo box directs Plk1 to specific cellular locations and is required together with protein kinase activity to promote cell proliferation. Plk1 localizes to centrosomes and the spindle poles at metaphase, in the central spindle during anaphase, and at the midbody during cytokinesis. Plk1 has been implicated in centrosome maturation, bipolar spindle formation and activation of the anaphase-promoting complex.
We have determined that intramolecular interactions of the catalytic and non-catalytic domains, as well as phosphorylation of Plk1 regulate the activation of its protein kinase activity. Our use of small interfering RNA to deplete Plk1 in cells demonstrates that it is required for centrosome duplication, anaphase and cytokinesis in mammalian cells. Cancer cells depleted of Plk1 rapidly undergo apoptosis. We are investigating whether this occurs in a wide variety of tumor cells or normal cells, as Plk1 may be a useful chemotherapy target.
A major effort in our laboratory is directed at identification and characterization of Plk1 substrates. Mitotic motor proteins, including the mitotic kinesin-like protein (MKLP1/CHO1), are of special interest. We also study the changes in function of substrates after mutation of sites phosphorylated by Plk1.
Joan S Brugge – Generation of antibody for identification of a transformation-specific protein: The putative avian sarcoma virus (ASV) src gene product Nature 1977 269 346-348
Identification of a transformation-specific antigen induced by an avian sarcoma virus (PDF)
Tony Purchio, Eleanor Erikson – Identification of the ASV src gene product by in vitro translation of the viral src gene PNAS 1978 75 (3) 1567-71
Identification of a polypeptide encoded by the avian sarcoma virus src gene (PDF)
Marc S Collett – Demonstration of src gene product protein kinase activity PNAS 1978 75 (4) 2021-24
Protein kinase activity associated with the avian sarcoma virus src gene product (PDF)
Eleanor Erikson – Synthesis of protein kinase activity by in vitro translation of viral src gene RNA Nature 1978 274 919-21
In vitro synthesis of a functional avian sarcoma virus transforming-gene product (PDF)
Marc S Collett, Joan S Brugge, Eleanor Erikson – A normal cell protein structurally and functionally related to the ASV src gene product Cell 1978 15 1363-69
Characterization of a normal avian cell protein related to the avian sarcoma virus transforming gene product (PDF)
Steve W Jones, Eleanor Erikson – Molecular cloning of a ribosomal S6 protein kinase PNAS 1988 85 3377-81
A Xenopus ribosomal protein S6 kinase has two apparent kinase domains that are each similar to distinct protein kinases (PDF)
Craig Crews – Purification, characterization and cloning of MEK, a protein kinase that phosphorylates and activates MAP kinase Science 1992 258 478-480
The primary structure of MEK, a protein kinase that phosphorylates the ERK gene product (PDF)
Daniel L Simmons – Gene expression in ASV-transformed cells: Molecular cloning in Cox2 and polo-like kinase PNAS 1991 88 2692-92
Expression of a mitogen-responsive gene encoding prostaglandin synthase is regulated by mRNA splicing (PDF)
Benjamin G Neel, Daniel L Simmons – Molecular cloning and gene expression of polo-like kinases Mol Cell Biol 1992 12 4164-96
Identification of an early-growth-response gene encoding a novel putative protein kinase (PDF)
Kyung S Lee – Pioneering studies on the structure and function of polo-like kinase1 PNAS 1998 95 9301-06
Mutation of the polo-box disrupts localization and mitotic functions of the mammalian polo kinase Plk (PDF)
Xiaoqi Liu, Hyungshin Yim – Demonstration that cancer cells are addicted to hight levels of Plk1 expression
PNAS 2003 100 5789-94
Polo-like kinase (Plk)1 depletion induces apoptosis in cancer cells (PDF)
Mol Cell Biol 2006 26 2093-108
Normal cells, but not cancer cells, survive severe Plk1 depletion (PDF)