Molecular Biology and Genetics MS Thesis Defense by Erdem Şanal



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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

MOLECULAR BIOLOGY AND GENETICS

MS THESIS DEFENSE BY ERDEM ŞANAL

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Title: Quantitative and Network Analysis of Cytokinesis Specific Phosphoproteins

 

Speaker: Erdem Şanal

 

Time: August 16th, 2017, 11:00

 

Place: ENG 127

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Asst. Prof. Dr. Nurhan Özlü (Advisor, Koc University)

Asst. Prof. Dr. Ayşe Koca Çaydaşı (Koc University)

Asst. Prof. Dr. Nurcan Tunçbağ (Middle East Technical University)

Abstract:

 

Nuclear division (mitosis) phosphorylation events are characterized extensively however phosphorylation events taking place during cytoplasmic division (cytokinesis) and responsible kinases are not well characterized. Using monopolar cytokinesis which is similar to bipolar cytokinesis in terms of cytoskeleton organization and phenotype, we identified phosphorylation events that are specific to cytokinesis. Our mass spectrometry analysis revealed that ~1500 phosphorylation events are present during cytokinesis. To identify responsible kinases that are active during cytokinesis, we have used Networkin 3.0, a kinase-substrate prediction algorithm, on our dataset. Including previously known cell cycle regulator kinases such as MAPK, CDK1/2 and Aurora, total 31 kinases were predicted to be active during cytokinesis. We also identified phosphorylation sites that are only present during cytokinesis in MKI67 protein which is reported as proliferation marker. MKI67 localizes to chromosomes during mitosis, acting as a surfactant which prevents chromosome condensation during mitosis.  These phosphorylation sites of the protein is found in successive repeat regions. We suggest that these cytokinesis specific phosphorylation of MKI67 might be important for its function in cell division.

Further we compared monopolar and bipolar cytokinesis to reveal phosphoproteomic differences using dimethyl labeling and mass spectrometry. Differentially regulated phosphoproteins’ functional analysis revealed sub protein networks for monopolar and bipolar cytokinesis that are functioning in cytoskeleton organization, midbody and cleavage furrow formation and mitotic nuclear division.

Lastly, we compared evolutionary conservation scores of phosphorylation sites that are specific to monopolar and bipolar cytokinesis to understand if differing phosphorylation events between two models are crucial. We observed no significant difference between two models, meaning monopolar cytokinesis specific phosphorylation events are not redundant.