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Title: Functional analysis of HIRA, a putative transcriptional regulator
Author: Farmer, Hannah Louise
ISNI:       0000 0001 3457 6735
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2001
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HIRA was isolated during positional cloning of the region of chromosome 22ql1 commonly deleted in DiGeorge Syndrome (DGS), a complex developmental anomaly thought to arise from the failure of neural crest cells to migrate or interact properly during early development. HIRA is a good candidate for a gene contributing to DGS, since Hira expression is particularly high in the developing neuroepithelium and the rostral neural crest. Hira -/- knockout mice indicate a critical role for Hira during development, demonstrating embryonic lethality by E10 with a wide range of malformation. HIRA encodes a WD40 repeat protein with strong similarity to two yeast transcriptional co-repressors HIR1 and HIR2, and the chromatin assembly factor CAF1 p60 subunit. HIRA also has similarity to the transcriptional co-repressor TUP1. Such homologies suggested HIRA might function as part of a protein complex, and a yeast two-hybrid screen of an early mouse embryonic library identified a number of potential HIRA interactors. Among these were several homeodomain-containing transcription factors including Pax3, Pax7 and Otx2, as well as core histones H3 and H2B. These interactions have been confirmed in vitro and the Pax3 interaction domain mapped. The effect of HIRA on Pax3- and Otx2-mediated transcription at target promoters has been investigated in cell transfection experiments. HIRA is able to stimulate Pax3-driven expression from the MITF promoter, yet a ternary complex between HIRA, Pax3 and DNA cannot be demonstrated by EMSA. HIRA has also been shown to stimulate transcription from several other unrelated promoters, suggesting that HIRA may effect transcription of a whole range of genes, although the mechanism by which this is achieved is unclear. Preliminary studies have been performed to examine HIRA-containing complexes to try to elucidate the mode of action of HIRA in transcriptional regulation. Sucrose gradient sedimentation analysis has revealed the presence of large HIRA- containing complexes and future work will focus on the analysis of these. Immunofluorescence studies in transfected cells reveal that HIRA shows a varied localisation pattern that may be under some sort of control. Preliminary data indicates that this may be related to the cell cycle, and this will be further investigated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: DiGeorge Syndrome; DGS: Cell cycle