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Title: Identification and charactisation of brcai interacting proteins.
Author: Ryan, Niamh Marie
ISNI:       0000 0001 3543 5491
Awarding Body: Queens University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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BRCA1 is a tumour suppressor gene (TSG), mutations ofwhich predispose to early-onset breast and ovarian cancer. Involvement ofBRCAl in DNA damage repair maintains chromosome stability. BRCA1 also participates in a variety of other pathways including: transcriptional regulation, ubiquitination, cell-cycle checkpoint control and apoptosis. BRCA1 mediates these functions by acting as a scaffold protein, allowing the assembly of multiprotein complexes. Yeast-2-Hybrid analysis is an in vivo technique for identifying protein:protein interactions. A yeast-2-hybrid screen was undertaken using an ovarian eDNA library and an N-terminal BRCA1 'Bait', composed ofthe amino acid residues 1-1142. The aim ofthe yeast-2-hybrid screen was to identify novel protein binding partners ofBRCAl. We identified two novel BRCA1 interacting proteins, which were confirmed by endogenous co-immunoprecipitation with BRCA1 in mammalian cells. These were the bromodomain containing protein 7 (BRD7) and the DExDIH box RNA helicase 36 (DHX36). Due to time constraints, the association between BRCA1 and DHX36 was not investigated further. BRD7 is a bromodomain containing protein whose main role appears to be in transcriptional regulation. We have demonstrated that both BRCA1 and BRD7 affect the transcription ofknown transcripts associated with the basallike subtype ofbreast cancer. BRCA1 transcriptionally represses expression ofKRT5, KRT17 and p-cadherin. Specifically, a BRCA1:c-Myc co-repressor complex is present at the promoter ofthese basal genes. We have shown that inhibition ofendogenous BRD7. expression, in the presence of functional BRCA1, abrogates expression ofthe BRCA1regulated KRT5 and p-cadherin basal marker genes. Further work is necessary to fully Supplied by The British Library - 'The world's knowledge' elucidate the mechanism and biological significance of this mode oftranscriptional regulation. Co-immunoprecipitation experiments also demonstrated an unexpected association between BRD7 and DHX36. Therefore, as well as the ability ofBRD7 and DHX36 to interact separately with BRCAl, it is possible that all three ofthe above proteins form a novel multimeric protein complex. Proving the existence ofthis BRCAl:BRD7:DHX36 multimeric complex and determination ofits function has still to be investigated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available