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Isolation of copy number suppressors of the nimA1kinase and mitotic regulation of nucleolar structure in Aspergillus nidulans

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2007, Doctor of Philosophy, Ohio State University, Molecular Genetics.
Regulation of cell cycle is critical for normal development of multicellular organisms and an understanding of this process is crucial for studying cell proliferation and cancer. A number of cell cycle dependent protein kinases specifically control mitotic progression and chromosome segregation. The nimAgene in Aspergillus nidulansencodes one such protein kinase that is both required and sufficient for chromosome condensation, spindle formation and nuclear pore disassembly to allow tubulin and regulators to enter nuclei during mitosis. In the filamentous fungus A. nidulans, the NIMA kinase is required for the regulation of mitosis along with CDK1/cyclin B. Levels of NIMA are regulated throughout the cell cycle, reaching a maximum at mitotic entry and falling dramatically at mitotic exit. The essential function of NIMA in A. nidulansand the growing recognition of its function in other eukaryotes, means that a study of NIMA function would reveal unique insights into cell cycle regulation among a broad range of organisms. I describe here the characterization of 3 novel genes mcnA, mcnBand mcnC, multi-copy number suppressors of the nimA1conditional mutant, identified in a copy number suppression screen of the nimA1mutant, and describe the potential novel roles they may play in mitotic regulation. I also present a study on the mitotic segregation of the nucleolus in A. nidulans. The nucleolus is a prominent nuclear structure whose mitotic segregation is poorly understood. In A. nidulansnuclei, mitosis is a partially open process and the nucleolus segregates through a completely novel mechanism. Unlike Saccharomyces cerevisiae, few A. nidulansnucleolar proteins segregate with DNA. Instead during DNA segregation, a double pinch of the NE occurs resulting in the formation of two daughter nuclei and a central cytoplasmic structure, the nuclear remnant, containing the nucleolus. While the NOR segregates with DNA, the bulk of nucleolar proteins remain distinct in the cytoplasm within the nuclear remnant. It is only during late telophase/early G1 that the nucleolar proteins from the remnant begin to undergo a sequential disassembly and reassembly into the daughter nuclei resulting in the formation of two functional daughter nucleoli by a step-wise process.
Stephen Osmani (Advisor)
239 p.

Recommended Citations

Citations

  • Ukil, L. (2007). Isolation of copy number suppressors of the nimA1kinase and mitotic regulation of nucleolar structure in Aspergillus nidulans [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1196234699

    APA Style (7th edition)

  • Ukil, Leena. Isolation of copy number suppressors of the nimA1kinase and mitotic regulation of nucleolar structure in Aspergillus nidulans. 2007. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1196234699.

    MLA Style (8th edition)

  • Ukil, Leena. "Isolation of copy number suppressors of the nimA1kinase and mitotic regulation of nucleolar structure in Aspergillus nidulans." Doctoral dissertation, Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1196234699

    Chicago Manual of Style (17th edition)