Cell Cycle and Tumorigenesis
Kerem Esmen, DVM, Specialist
Mehmet Ergüven, MSc Student
Muhammet Memon, MSc Student
We are interested in elucidating the molecular mechanisms that regulate the mitotic transition. Of particular interest to us is the interplay between the kinases and phosphatases that ensure the introduction/ removal of phosphates to/from the mitotic proteins takes place in correct order and in a timely manner. Another branch of our research focuses on the generation of mouse models that mimic human liver cancer development in vivo.
In addition to basic research, our lab contributes to technology transfer at iBG by the development of biosimilars for biotherapeutic mAbs.
1-Regulation of mitosis by kinases and phosphatases: Progress through different phases of the cell cycle is regulated by concerted actions of CDKs in complexes with their partner cyclin molecules. Mitotic entry and progression are regulated by Cdk1/Cyclin B1 complexes. Mitosis phase of the cell cycle involves a number of irreversible major cellular events such as nuclear envelope breakdown and chromosome condensation. Therefore, the mitotic entry has to be regulated very tightly by a variety of regulatory mechanisms, whose aim is to ensure a total inhibition of Cdk1 kinase activity prior to mitosis. During mitotic entry, Cdk1 activity rises and falls very sharply in a switch-like mechanism. Cdk1 utilizes several effector kinases to phosphorylate mitotic substrates. On the other hand, dephosphorylation by phosphatases has to be prevented for an efficient accumulation of phosphorylations on these substrates. We study the molecular interplay between Cdk1, its effector mitotic kinases and mitotic phosphatases, utilizing transgenic animal models and cell lines derived from them or genetically engineered for this purpose.
2-Mouse models of liver cancer: From a simplified perspective, cancer can be described as a disorder of the cell cycle. Not surprisingly, cell cycle genes are frequently found to be deregulated during tumorigenesis. Cyclin-dependent kinases (CDKs) are positive regulators of cell cycle progression while cyclin-dependent kinase inhibitors (CKIs) work as brakes to stop cell division. Tumorigenesis results from abnormal expression or activation of positive regulators and/or practical suppression of negative regulators. Due to their critical roles in cell cycle, CDKs and CKIs have potential as druggable targets to stop or slow down tumorigenesis. We utilize mouse models to study roles of CDKs and CKIs in tumorigenesis. Liver tumors can be very efficiently developed in rodents by using the hydrodynamic tail vein injection protocol that introduces an oncogenic plasmid DNA cocktail including the Sleeping Beauty transposase, into the hepatocytes. Previously, we have shown that Cdk1 deficient livers are fully resistant to tumorigenesis. We aim to investigate the CDKs and CKIs as potential therapeutic targets in various tumors utilizing transgenic mouse models.
Several mechanisms regulate Cdk1 kinase activity. First and foremost, both Cdk1 and Cyclin B1 genes are targets of E2F transcription factors and are expressed only upon reception of mitogenic stimuli. Inhibitory phosphorylations, introduced by the inhibitory kinases Wee1 and Myt1, have to be removed by Cdc25 phosphatase and an activating phosphorylation has to be introduced by the Cdk-activating kinase for full Cdk1 activity (left panel). The overall outcome of these regulations is a “switch-like” mitotic state, whereby Cdk1 activity rises steeply during mitotic entry and falls sharply, as a result of Cyclin B1 degradation preceding mitotic exit (right panel).
Greatwall/Mastl kinase is one of the several effector kinases of Cdk1 in mitosis. It is activated by Cdk1 during mitosis and in turn, it phosphorylates two small inhibitory proteins Arpp19 and Ensa that sterically inhibit PP2A phosphatase activity. This regulatory pathway ensures accumulation of mitotic phosphorylations rapidly.We have generated a conditional knockout mouse model of the Mastl kinase. Mastl KO embryos die very early during development. Conditional deletion of Mastl prior to meiosis resulted in an arrest before metaphase II. In somatic cells, deletion of Mastl resulted in chromosome segregation defects during anaphase. We are investigating the molecular mechanisms underlying these phenotypes using transgenic mouse models and cell lines derived from them.
|2014 – present||Assistant Professor – Group Leader
Dokuz Eylul University, Izmir Biomedicine and Genome Institute/Center, Izmir, Turkey.
|2007 – 2014||Research Assistant
Institute of Molecular and Cell Biology, Singapur.
|2006 – 2007||Visiting Scholar
National Cancer Institute, Frederick, MD, ABD.
|2005 – 2006||Research Assistant
Free University, Berlin, Germany.
|2001 – 2005||PhD. in Molecular Biology
Georg-August University, Göttingen, Germany.
|2000 – 2001||MSc. in Molecular Biology
International Max Planck Research School, Göttingen, Germany.
|1996 – 2000||BS. in Molecular Biology and Genetics
Boğaziçi University, Istanbul, Turkey.
|AWARDS AND RECOGNITION
• Science Academy Young Scientist Awards Program (BAGEP) 2016 Award
• Scientific and Technological Research Council of Turkey (TUBITAK) Reintegration Fellowship
Full list and citations : Google Scholar : Kasim Diril
• Diril MK, Bisteau X, Kitagawa M, Caldez MJ, Wee S, Gunaratne J, Lee SH, Kaldis P. Loss of the Greatwall Kinase Weakens the Spindle Assembly Checkpoint. PLoS Genet. 2016 Sep 15;12(9):e1006310.
• Chauhan S, Diril MK, Lee JH, Bisteau X, Manoharan V, Adhikari D, Ratnacaram CK, Janela B, Noffke J, Ginhoux F, Coppola V, Liu K, Tessarollo L, Kaldis P. Cdk2 catalytic activity is essential for meiotic cell division in vivo. Biochem J. 2016 Sep 15;473(18):2783-98.
• Adhikari D, Diril MK, Busayavalasa K, Risal S, Nakagawa S, Lindkvist R, Shen Y, Coppola V, Tessarollo L, Kudo NR, Kaldis P, Liu K. Mastl is required for timely activation of APC/C in meiosis I and Cdk1 reactivation in meiosis II. J Cell Biol. 2014 Sep 22;206(7):843-853.
• Miettinen TP, Pessa HK, Caldez MJ, Fuhrer T, Diril MK, Sauer U, Kaldis P, Björklund M. Identification of transcriptional and metabolic programs related to mammalian cell size. Curr Biol. 2014 Mar 17;24(6):598-608.
• Kononenko NL, Diril MK, Puchkov D, Kintscher M, Koo SJ, Pfuhl G, Winter Y, Wienisch M, Klingauf J, Breustedt J, Schmitz D, Maritzen T, Haucke V. Compromised fidelity of endocytic synaptic vesicle protein sorting in the absence of stonin 2. Proc Natl Acad Sci U S A. 2013 Feb 5;110(6):E526-35.
• Diril MK, Ratnacaram CK, Padmakumar VC, Du T, Wasser M, Coppola V, Tessarollo L, Kaldis P. Cyclin-dependent kinase 1 (Cdk1) is essential for cell division and suppression of DNA re-replication but not for liver regeneration. Proc Natl Acad Sci U S A. 2012 Mar 6;109(10):3826-31.
• Diril MK, Schmidt S, Krauss M, Gawlik V, Joost HG, Schürmann A, Haucke V, Augustin R. Lysosomal localization of GLUT8 in the testis–the EXXXLL motif of GLUT8 is sufficient for its intracellular sorting via AP1- and AP2-mediated interaction. FEBS J. 2009 Jul;276(14):3729-43.
• Diril MK, Wienisch M, Jung N, Klingauf J, Haucke V. Stonin 2 is an AP-2-dependent endocytic sorting adaptor for synaptotagmin internalization and recycling. Dev Cell. 2006 Feb;10(2):233-44.