Genetic and functional characterization of the interaction of BRCA1 with the serine/threonine phosphatase, PP1, and the circadian clock proteins, Per1 and Per2
By: by Sherry Lynn Winter.
Published: 2006
Language: eng
Number of pages: 164
ISBN-13: 9780494160213
Description: A tumour-associated missense mutation in BRCAI abrogates its interaction with both Per1 and Per2. Preliminary analysis of this interaction suggests that BRCA1 interacts with Per2 following treatment of cells with gamma-irradiation. Additionally, analysis of the expression levels of Per1 and  2 in relation to other genes that may be involved in the development of breast cancer indicates that their expression correlates significantly with that of BARD1, suggesting that the ubiquitinating role of the BRCA1/BARD1 heterodimer may be an important mediator of Per1 and 2 functions.The breast cancer susceptibility gene, BRCA1, is implicated in multiple cellular processes including DNA repair, the transactivation of genes and maintenance of centrosomes. To further elucidate the function and regulation of BRCA1, I have characterized protein interactions with BRCA1 that were previously identified in a yeast two-hybrid study. Protein Phosphatase 1beta (PP1beta), a serine threonine phosphatase, and the Circadian Clock proteins Per1 and Per2, interact with protein encoded by exon11 of BRCA1 and may, therefore, be involved in the development of breast cancer.Further characterization of the interaction of BRCA1 with PP1 revealed that BRCA1 also coimmunoprecipitates with PP1alpha, beta or gamma. Use of BRCA1-GST fusion proteins identified the region as well as the specific PP1 interacting domain in BRCA1 mediating their interaction. PP1 dephosphorylates BRCA1 in an in vitro phosphatase assay, and colocalization studies indicate that BRCA1, along with PP1alpha or beta, interact at the centrosome during mitosis along with other proteins such as Aurora-A kinase and gamma-tubulin. The balance of kinase and phosphatase activity at the centrosome can have important consequences on its function and regulation. Consequently, I analyzed expression levels of the three PP1 isoforms, along with additional genes encoding proteins with centrosomal functions to elucidate their relationship with each other and centrosome amplification in breast tumours. I found a strong correlation between the expression of PP1 alpha and beta with that of gamma-tubulin. BRCA1 may regulate the function of PP1 at the centrosome, and loss of this regulation could result in aneuploidy, a common phenotype of breast tumours lacking functional BRCA1.
Notes: Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3604.

Thesis (Ph.D.)--University of Toronto, 2006.

Includes bibliographic references.

Electronic version licensed for access by U. of T. users.