The role of Schizosaccharomyces pombe Orb6p in cell morphogenesis and cell cycle regulation

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Biochemistry and Molecular Biology

First Committee Member

Kenneth Rudd - Committee Chair


Orb6p from Schizosaccharomyces pombe is a 55 kD, serine/threonine protein kinase that has a role in the maintenance of polarized cell growth during interphase and also functions as a negative regulator of mitosis. In order to better understand how Orb6p functions in S. pombe, three primary goals were pursued: (1) Identification of cellular proteins that functionally interact with Orb6p; (2) Identification and characterization of proteins that physically interact with Orb6p kinase; (3) Development of a method for identifying Orb6p substrates. Several techniques were employed in order to accomplish these goals, including the use of synthetic lethality experiments, multi-copy suppression screens, and a two-hybrid screen. A number of proteins were identified that functionally interact with Orb6p in the control of cell polarity during interphase and in the control of cellular entry into mitosis. These proteins include Bgs4p, Pak1p/Shk1p, Bot1p, Mob2, Sum3p/Ded1p, Skb1p, Mor2p, and Rio1p/Rga4p. A better understanding of how Orb6p functions in S. pombe was achieved by the analysis and classification of these protein interactions into five groups: (1) Control of Orb6p kinase activity; (2) Localization of Orb6p to the cell tip(s); (3) Establishment and maintenance of cell polarity and the actin cytoskeleton; (4) Cell cycle control; (5) Control of cell wall formation. Lastly, a novel experimental approach for the identification of Orb6p kinase substrates was detailed, which allows for further research in understanding how Orb6p functions in S. pombe.


Biology, Molecular; Biology, Cell

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