생명과학과·I-Bio 특별세미나 안내

[Announcement on Life Sciences·I-Bio Special Seminar (1) ]
         
           
        ▶Subject: Understanding complex enzymatic networks: from MAPK to PKR
        
        ▶Speaker: Yoosik Kim, Ph.D.(Postdoctoral Research, Seoul National Univ.)
                
        ▶Date: 15:00~16:00 /Dec./8(Mon)/2014
               
        ▶Place: Auditorium(1F), POSTECH Biotech Center
               
                *Abctract
             The development and maintenance of living tissues relies on cell communication systems, which, to a first order approximation, can be viewed as large networks of enzymatic reactions. Quantitative analysis of these networks holds the key to the fundamental understanding of embryonic development, elucidating the origins of developmental disorders, and designing man-made tissues. In this talk, I will present our analysis of two enzymatic networks; Mitogen Activated Protein Kinase (MAPK) and interferon-induced dsRNA-dependent protein kinase (PKR).
MAPK is core of a conserved signaling pathway that regulates cellular processes in all eukaryotes. MAPK is activated when it is phosphorylated by an upstream kinase; this process is reversed by a specific phosphatase. Activated MAPK controls cellular processes by phosphorylating its multiple substrates, such as transcription factors and other enzymes. Using a combination of genetic experiments in the Drosophila embryo, quantitative imaging, and mathematical modeling approach, I found that the level of MAPK substrates can control the activation status of this enzyme and its ability to distribute its enzymatic activity among multiple substrates. Furthermore, I established that MAPK substrate competition is biologically significant and plays a key role in the regulation of gene expression and cell differentiation in the embryo.
In the second half of the talk, I will present our recent analysis of PKR in regulating mammalian cell cycle. PKR is a member of innate immune response genes that undergo activation via autophosphorylation when bound to viral dsRNAs during infection. I found that PKR is phosphorylated in uninfected cells during mitosis by binding to dsRNAs formed by inverted repeats of Alu. Phosphorylated PKR orchestrates mitotic processes and its disruption leads to misregulation of mitotic factors, delay in mitotic progression, and defects in cytokinesis. This work illustrates the physiological function of an immune response protein in uninfected cells and suggests function of cellular dsRNAs as signaling molecules during mitosis. Going beyond the cell cycle, I propose that dsRNAs and their interacting enzymes such as PKR compose important biomolecular networks that govern diverse cellular processes both in infected and normal cells
   
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