Jillian Youds

JILLIAN YOUDS- PhD DEFENSE

“Roles of the DOG-1 and JRH-1 helicase-like proteins in DNA repair in Caenorhabditis elegans”

B.Sc. Simon Fraser University, 2003
Thursday, November 22, 2007, 12:30pm Room 200, Graduate Student Centre
Jillian Youds- PhD Defense program- pfd

SUPERVISORY COMMITTEE

Dr. Ann Rose, Research Supervisor (Medical Genetics)
Dr. Peter Lansdorp (Medical Genetics)
Dr. Donald Riddle (Medical Genetics)
Dr. Hugh Brock (Zoology)

EXAMINING COMMITTEE

Chair: Dr. Robert Hancock (Microbiology and Immunology)
Supervisory Committee: Dr. Ann Rose, Research Supervisor (Medical Genetics), Dr. Peter Lansdorp (Medical Genetics)
University Examiners: Dr. Donald Moerman (Zoology), Dr. Robert Kay (Medical Genetics)
External Examiner: Dr. Phil Hartman, Department of Biology. Texas Christian University. Fort Worth, TX. USA

ABSTRACT

Helicases perform vital roles in the cell by unwinding DNA to make it accessible for the essential processes of replication, transcription and repair. In Caenorhabditis elegans, the DOG-1 helicase-like protein is required for polyG/polyCtract (G/C-tract) maintenance, as dog-1 animals have a mutator phenotype characterized by deletions that initiate in G/C-tracts. DOG-1 may unwind secondary structures that form in polyguanine DNA during lagging strand replication. In order to more completely understand the role of dog-1, genetic interactors were identified. dog-1 functionally interacts with the him-6/BLM helicase. Absence of recombinational repair-implicated proteins in the dog-1 background, including HIM-6/BLM, RAD-51, BRD-1/BARD1 and HIM-9/XPF, as well as the trans-lesion synthesis polymerases polk and polh increased the frequency of animals with G/C-tract deletions, indicating that these pathways are important mechanisms for repair at G/C-tracts in the absence of DOG-1. These data support the hypothesis that persisting DNA secondary structures can cause replication fork stalling, which can be resolved by deletion-free or deletion-prone mechanisms. DOG-1 has highest sequence identity to human BRIP1/FANCJ, which is mutated in patients from the Fanconi Anemia (FA) subgroup J. DNA damage sensitivity experiments indicated that, like chicken FANCJ cells, dog-1 mutants were not significantly sensitive to DNA damage from X-ray or UV-irradiation, but were extremely hypersensitive to the DNA interstrand cross-linking agent UVA-activated trimethylpsoralen. Thus, DOG-1 appears to have a conserved role in cross-link repair and is the C. elegans FANCJ homolog. Characterization of the dog-1/FANCJ related helicase, jrh-1, revealed that mutants for this putative helicase are moderately sensitive to cross-linking agents. dog-1 jrh-1 double mutants displayed a synthetic lethal phenotype characterized by excessive recombination intermediates and mitotic catastrophe in the germline. However, absence of JRH-1 did not have any effect on G/C-tract deletions, indicating that JRH-1 does not have a redundant function with DOG-1 at G/C-tracts. Absence of JRH-1 reduced the fitness of eT1 and nT1 translocation heterozygotes, but not translocation homozygotes. jrh-1 was synthetically lethal with him-6/BLM and with the endonuclease mus-81, suggesting a possible role for JRH-1 in regulating the balance between different types of repair.

PUBLICATIONS

Jillian L. Youds, Louise J. Barber, Jordan D. Ward, Spencer J. Collis, Nigel J.

O’Neil, Simon J. Boulton & Ann M. Rose (2007). DOG-1 is the Caenorhabditis elegans BRIP1/FANCJ homologue and functions in interstrand cross-link repair. In review at Molecular and Cellular Biology.

Jillian L. Youds, Nigel J. O’Neil & Ann M. Rose (2006). Homologous recombination is required for genome stability in the absence of DOG-1 in Caenorhabditis elegans. Genetics 173(2): 697-708.

Yang Zhao, Kenneth Lai, Iris Cheung, Jillian Youds, Maja Tarailo, Sanja Tarailo & Ann Rose (2006). A mutational analysis of Caenorhabditis elegans in space. Mutation Research 601(1-2): 19-29.

PRESENTATIONS

Jillian L. Youds, Louise J. Barber, Jordan D. Ward, Spencer J. Collis, Nigel J. O’Neil, Simon J. Boulton & Ann M. Rose. Characterization of BRIP1/FANCJ homologs in ICL repair in Caenorhabditis elegans. Invited speaker and poster presentation at the Keystone Symposium for Genome Instability and DNA Repair. Breckenridge, Colorado, January 17-22, 2007.

Louise J. Barber, Jillian L. Youds, Jordan D. Ward, Spencer J. Collis, Julie S. Martin, Nigel J. O’Neil, Ann M. Rose & Simon J. Boulton. Identification of a novel helicase involved in Fanconi Anaemia Repair. Poster presented at the 18th Annual Fanconi Anemia Scientific Symposium. Bethesda, Maryland, October 19-22, 2006.

Jillian L. Youds, Nigel J. O’Neil, Louise J. Barber, Simon J. Boulton & Ann M. Rose. The DOG-1 helicase, genomic instability and Fanconi anemia. Poster presented at the European Worm Meeting. Hersonissos, Greece, April 29-May 3, 2006.

Jillian L. Youds, Nigel J. O’Neil and Ann M. Rose. The Caenorhabditis elegans dog-1 mutant as a model for Fanconi anemia. Poster presented at the GSA Genetic Analysis: Model Organisms to Human Biology meeting. San Diego, California, January 5-7, 2006.

Jillian Youds, Nigel O’Neil & Ann Rose. Absence of DOG-1 triggers cep-1-mediated apoptosis in Caenorhabditis elegans. Poster presented at the C. elegans International Meeting. Los Angeles, California, June 25-29, 2005.

Jillian L. Youds, Iris Cheung & Ann M. Rose. The helicases DOG-1 and HIM-6 function synergistically to maintain genome stability in Caenorhabditis elegans. Poster presented at the Keystone Symposia on Genome Instability and DNA Repair. Taos, New Mexico, March 15-20, 2005.

Jillian L. Youds & Ann M. Rose. 2004. Functional interactions with DOG-1. Poster presented at the West Coast Worm Meeting. Santa Barbara, California, August 21- 24, 2004.

AWARDS

2007-2008 National Cancer Institute of Canada/Terry Fox Foundation Graduate Fellowship
2007-2008 Michael Smith Foundation Senior Trainee Award
2007 Keystone Symposia Travel Award
2004-2007 NSERC PGS-D Scholarship
2004-2006 Michael Smith Foundation Junior Trainee Award
2005 Keystone Symposia Travel Award
2003-2004 NSERC CGS-M Scholarship
2003-2004 Medical Genetics Entrance Scholarship

Courses

MEDG505: Genome Analysis, Drs. S. Jones & P. Hieter
MEDG520: Human Molecular Genetics, Dr. R. McMaster
MEDG521: Biology and Genetics of Neoplasm, Dr. P. Hoodless
MEDG530: Advanced Human Genetics, Dr. J. Friedman
MEDG545: Current Topics in Genomics, Dr. A. Brooks-Wilson
MEDG548: Directed Studies, Dr. A. Rose

Jillian Youds- PhD Defense program- pfd