Yeast and mammalian cell cycle regulation; Regulation of mitotic exit, cytokinesis, daughter cell-specific gene expression, and polarized growth.
Key words: yeast, cell cycle, mitosis, cytokinesis, cell polarity, daughter cell-specific gene expression, mitotic checkpoint regulation, kinetochore, Mitotic Exit Network (MEN), Regulation of Ace2-dependent transcription and Morphogenesis (RAM).
Description of Research
The Luca lab studies conserved signaling networks that coordinate the diverse cellular processes associated with cell division and cellular morphogenesis. The lab employs multidisciplinary approaches, including yeast genetics, biochemistry and cellular and molecular biology to investigate the conserved functions of the Mob protein family. The budding yeast Saccharomyces cerevisiae expresses two Mob proteins, Mob1 and Mob2, that function in distinct pathways.
Mob1 and MEN
Mob1 is a component of the conserved Mitotic Exit Network (MEN), which coordinates events associated with the M to G1 transition, such as cyclin dependent kinase (CDK) inactivation, spindle disassembly, cytokinesis and G1 gene transcription. Mob1 is a regulatory subunit of the MEN protein kinase Dbf2, which is related to the poorly understood human LATS tumor suppressor. Both Mob1 and Dbf2 localize to mitotic spindle poles and the cytokinesis ring during mitotic exit. Mob1 and Dbf2 kinase appear to mediate mitotic exit by activating Cdc14 phosphatase, which antagonizes the mitosis inducing activity of CDK. In addition, Mob1 and Dbf2 are important for triggering cytokinesis and septum formation. Intriguingly, Mob1 also interacts with Mps1 kinase, which regulates mitotic checkpoint function and centrosome duplication. Currently, we are trying to establish how Mob1-Dbf2 kinase regulates Cdc14 phosphatase and cytokinesis.
Mob2 and RAM
We recently discovered that Mob2 is a component of a conserved signaling network, termed RAM for Regulation of Ace2-dependent transcription and Morphogenesis. The RAM network is comprised of at least six proteins that regulate: 1) polarized growth by maintaining the polarity of the actin cytoskeleton; 2) the localization and activity of Ace2 transcription factor, which regulates transcription of a subset of genes in the daughter cell; and 3) maintenance of cell wall integrity. Mob2 binds to and regulates Cbk1, a Dbf2-related protein kinase. Both Mob2 and Cbk1 localize to sites of cortical growth and, remarkably, to the daughter cell nucleus. Our data suggests that the Mob2-Cbk1 complex acts late in the RAM signaling network and directly regulates the daughter cell-specific localization and function of Ace2 transcription factor. Thus, the RAM signaling network provides a novel mechanism for yeast cells to regulate differential gene expression. This work has important implications regarding mechanisms for controlling development in multicellular organisms. We are currently investigating the mechanisms of RAM in regulating polarized growth and daughter-specific gene expression.
Mammalian MEN and RAM
Because most MEN and RAM proteins are highly conserved, we expect that MEN- and RAM-like signaling networks will be critical for regulating cell division and development in all eukaryotes. Thus, in addition to exploring the functions of MEN and RAM signaling networks in yeast, we are expanding our research to investigate the roles of related signaling networks in mammalian cells. Collectively, research regarding Mobs, MEN and RAM will help resolve the regulatory mechanisms of cell division and cancer development.
Many rotation projects are available involving a variety of approaches. Some examples are:
1. Investigate the role of MEN and RAM in regulating cytokinesis, cell polarity, genomic stability and gene expression.
2. Genetic and biochemical approaches to identify regulators and substrates of MEN and RAM.
3. Characterization of MEN and RAM protein complexes
4. Structure-function analysis of MEN and RAM proteins and kinases.
5. Analysis of MEN or RAM protein dynamics in live cells by fluorescence recovery after photobleaching (FRAP).
Cornelia Kurischko, Ph.D. - Research Specialist
V. Kasinath Kuravi, Ph.D. - Postdoctoral Fellow
Hongkyung KIm, Ph.D. - Postdoctoral Fellow
Diane Raines - Lab assistant
Kurischko C., Weiss G., Ottey M., Luca FC. A Role for the Saccharomyces cerevisiae Regulation of Ace2 and Polarized Morphogenesis Signaling Network in Cell Integrity Genetics 171: 443-55, 2005.Bothos J., Tuttle RL., Ottey M., Luca FC., Halazonetis TD. Human LATS1 is a mitotic exit network kinase Cancer Research 65: 6568-75, 2005.Kurischko Cornelia, Kuravi Venkata K, Wannissorn Nattha, Nazarov Pavel A, Husain Michelle, Zhang Chao, Shokat Kevan M, McCaffery J Michael, Luca Francis C The yeast LATS/Ndr kinase Cbk1 regulates growth via Golgi-dependent glycosylation and secretion. Molecular biology of the cell 19: 5559-78, 2008.Tuttle Robyn L, Bothos John, Summers Matthew K, Luca Francis C, Halazonetis Thanos D Defective in mitotic arrest 1/ring finger 8 is a checkpoint protein that antagonizes the human mitotic exit network. Molecular cancer research : MCR 5: 1304-11, 2007.Stoepel Jan, Ottey Michelle A, Kurischko Cornelia, Hieter Philip, Luca Francis C The mitotic exit network Mob1p-Dbf2p kinase complex localizes to the nucleus and regulates passenger protein localization. Molecular biology of the cell 16: 5465-79, 2005.Luo Guangzuo, Zhang Jian, Luca Francis C, Guo Wei Mitotic phosphorylation of Exo84 disrupts exocyst assembly and arrests cell growth. The Journal of cell biology 202: 97-111, 2013.Saputo Sarah, Chabrier-Rosello Yeissa, Luca Francis C, Kumar Anuj, Krysan Damian J The RAM network in pathogenic fungi. Eukaryotic cell 11: 708-17, 2012.Kuravi Venkata K, Kurischko Cornelia, Puri Manasi, Luca Francis C Cbk1 kinase and Bck2 control MAP kinase activation and inactivation during heat shock. Molecular biology of the cell 22: 4892-907, 2011.Kurischko Cornelia, Kuravi Venkata K, Herbert Christopher J, Luca Francis C Nucleocytoplasmic shuttling of Ssd1 defines the destiny of its bound mRNAs. Molecular microbiology 81: 831-49, 2011.Kurischko Cornelia, Kim Hong Kyung, Kuravi Venkata K, Pratzka Juliane, Luca Francis C The yeast Cbk1 kinase regulates mRNA localization via the mRNA-binding protein Ssd1. The Journal of cell biology 192: 583-98, 2011.