Dissertation/Thesis Abstract

Structural and Functional Study of the Interaction Between Ki67 FHA Domain and NIFK
by Song, Haiyan, Ph.D., The Ohio State University, 2008, 141; 10631276
Abstract (Summary)

Ki67 is a nuclear protein that is over-expressed in proliferating cells. It is believed to be involved in the regulation of rRNA gene transcription and cell proliferation. In this dissertation, efforts have been made to understand both the structural basis and the biological function(s) of the interaction between the FHA domain from Ki67 and the nucleolar protein NIFK. Previous studies showed that Ki67 FHA domain binds to a phosphopeptide consisting of NIFK amino acid residues 226 to 269. NIFK (226-269) can be sequentially phosphorylated by kinases CDK1/cyclin B and GSK3β at Thr238 and Thr234, respectively, in vitro. In this work, we explored the sequential phosphorylation mechanism of NIFK (226-269) by CDK1/cyclin B and GSK3β, and revealed that the proline residues around Thr234 and Thr238 directly regulate the kinase recognition specificities. We also probed the molecular mechanism controlling the multisite interaction between the Ki67 FHA domain and NIFK (226-269)_3p. Our results showed that the Ki67 FHA domain-NIFK (226-269)_3p interaction involves three factors: the local recognition of the phosphate group from phospho-Thr234, an extended hydrophobic interface in the middle of the NIFK peptide, and the extension of the β-sheet of the FHA domain by the addition of a β-strand formed by NIFK (260-269).

To further shed a light on the biological functions of the Ki67 FHA domain-NIFK (226-269)_3p interaction, a proteomics study was performed to define the NIFK interactome. NIFK was shown to interact with B23, an important nucleolar protein involved in ribosome biogenesis, in an RNA and cell cycle-dependent manner. Ki67 may modulate this interaction via its FHA domain in mitosis. The NIFK interacting proteins were primarily ribosomal proteins and proteins involved in ribosome biogenesis. NIFK was also found to be associated with pre-rRNAs. Knockdown of NIFK gene expression caused accumulation of cells at the G1/S transition in cell cycle progression. Together, these findings suggest that NIFK may function coordinately with Ki67 and B23 in ribosome biogenesis and cell proliferation. Ki67 may regulate and maintain the balance between ribosome biogenesis and cell cycle progression, by regulating the NIFK-B23 interaction in a cell cycle-dependent manner.

Indexing (document details)
Advisor: Tsai, Ming-Daw
Commitee: Dalbey, Ross, Jhiang, Sissy, Vandre, Dale
School: The Ohio State University
Department: Biochemistry
School Location: United States -- Ohio
Source: DAI-B 78/11(E), Dissertation Abstracts International
Subjects: Cellular biology, Biochemistry
Keywords: B23, Fha domain, Ki67, Nifk
Publication Number: 10631276
ISBN: 978-0-355-01544-7
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