Dr. Philip Hieter, Research Supervisor (Medical Genetics)
Dr. Carolyn Brown (Medical Genetics)
Dr. Ann Rose (Medical Genetics)
Dr. Michel Roberge (Biochemistry and Molecular Biology)
EXAMINING COMMITTEE
Chair: Dr.
David Kitts (Food Science)
Supervisory
Committee: Dr. Philip Hieter, Research Supervisor (Medical Genetics),
Dr. Carolyn Brown (Medical Genetics), Dr. Michel Roberge (Biochemistry and
Molecular Biology)
University
Examiners: Dr. James Kronstad (Microbiology and Immunology), Dr.
Peter Lansdorp (Medicine)
External
Examiner: Dr. Douglas Koshland, Department of Embryology, Carnegie
Institution. Baltimore, MD, USA.
ABSTRACT
During the course of the mitotic cell cycle, the genetic
material must be faithfully replicated and segregated to daughter cells.
After DNA replication when chromosomes have been duplicated, each pair of identical
sister chromatids must remain tethered together until all pairs of sister centromeres have attached to the mitotic spindle in a bi-oriented manner, a state termed
metaphase. Once metaphase has been successfully achieved, the initiation
of anaphase can take place, and sister chromatids are pulled apart to the two
daughter cells. Errors in this process lead to chromosome missegregation (chromosome loss
or non-disjunction) and result in aneuploidy, which may have deleterious
effects. Processes important in chromosome segregation fidelity include kinetochore
attachment to the spindle and sister chromatid cohesion. A genome wide two hybrid
screen using SGT1 as the “bait” identified a previously uncharacterized open
reading frame, YDR014W (RAD61) that, when deleted, missegregated a chromosome
fragment. YDR014W corresponded to the gene encoding the complementation group,
CTF6, and was also recently characterized as RAD61 in a screen for deletion mutants
sensitive to ionizing radiation. rad61 delete diploid mutant strains displayed a G2/M
progression delay dependent on Mad2p and were hypersensitive to DNA damaging
agents. Rad61p localizes to the nucleus and a fraction binds chromatin.
Rad61p is not a core component of the yeast kinetochore and is not required for
homologous recombination repair of DNA damage, but is important for
sister chromatid cohesion. Using co-immunoprecipitation and mass
spectrometry analysis, we identified a protein-protein interaction between Rad61p
and Ded1p, an RNA helicase of the DEAD box family that has important roles in
initiation of translation and mRNA splicing. Ded1p binds chromatin and may have direct
roles in chromosome biology. A temperature sensitive allele of the essential
DED1 gene causes an increased rate of chromosome missegregation. rad61 delete and
ded1 temperature sensitive alleles displayed conditional synthetic
lethality, indicating that the interaction is functionally significant within
yeast cells. Taken together, these results suggests that Rad61p and Ded1p function together in the
nucleus for processes that are important for sister chromatid cohesion and for
chromosome segregation.
PUBLICATIONS
Measday V, Baetz K, Guzzo J, Yuen K, Shiekh B, Kwok T, Ueta
R, Hoac T, Cheng B, Pot I,
Tong A, Yamaguchi-Iwai Y, Boone C, Hieter P, Andrews B. (2005) Genomic Dissection of the Yeast Kinetochore Identifies a
Role for the Iron Responsive Transcription Factor Rcs1 in Chromosome
Stability. Proc Natl Acad Sci USA. In press.
Andrew SE, McKinnon M, Cheng BS, Francis A, Penney J, Reitmar AH, Mak TW, Jirik FR. (1998) Tissues of MSH2-deficient mice
demonstrate hypermutability on exposure to a DNA methylating agent. Proc Natl Acad Sci
USA Feb 3; 95(3): 1126-1130.
PRESENTATIONS
Cheng B, Kitagawa K, Hieter P (2003) Analyzing the Role of
RAD61/CTF6 (YDR014W) in Chromosome Segregation. Poster presentation
at the Cold Spring Harbour Yeast Cell Biology Meeting. Cold Spring Harbour
Laboratories, NY, USA. August 2003.
Cheng B, Kitagawa K, Hieter P. (2001) Characterization of
a Novel Two Hybrid Interactor of SGT1. Poster presentation at the Salk Cell
Cycle Meeting. San Diego, CA, USA. June 2001.
AWARDS
2000-2003 CIHR Doctoral Research Award
2000-2001 UBC Killam Predoctoral Fellowship
1998-2000 NSERC PGS A Scholarship
1997-1998 Simon Fraser University Open Scholarship
1992-1996 Simon Fraser University Chancellor’s Entrance
Scholarship
GRADUATE STUDIES
Field of
Study: Chromosome segregation in budding yeast
Courses:
BIOC 521 Advanced Topics in Molecular Biology, Dr. M.
Roberge
MEDG 505 Genome Analysis, Drs. P. Hieter and A. Rose
MEDG 520 Advanced Human Molecular Genetics, Dr. C. Brown
MEDG 521 Biology and Genetics of Neoplasia, Dr. V. Ling
MEDG 530 Advanced Human Genetics, Dr. J. Friedman
MEDG 540 Medical Genetics Seminar, Drs. C. Brown and F.
Dill
