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Date of Award


Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

Craig Vierra

First Committee Member

Joan Lin Cereghino

Second Committee Member

David Thomas


Basic helix-loop-helix transcription factors play important roles in pathways that result in the formation of such tissues as skeletal muscle, the nervous system, pancreas and heart. A recently discovered B-cell restricted bHLH transcription factor activated Bcell factor 1 (ABF -1) is suspected to play a role in the regulation of B cell differentiation. ABF -1 was initially characterized as being a transcriptional repressor because it was able to prevent the transactivation abilities of E47 in HeLa cells and the region responsible was hypothesized to reside within the C-terminal portion. This study has further mapped the repression domain to the C-terminal portion bearing the bHLH domain. In addition, we report the discovery of a region in the N-terminus that has a secondary negative effect on the transactivation ability of E2A. To complement these studies, the subcellular localization and nuclear localization signal of GFP-tagged ABF -1 proteins was performed using fluorescent microscopy. These studies suggest that ABF-1 exerts it function through the bHLH domain and the region of the nuclear localization signal lies within amino acids 71-103. Taken together, the ability of the C-terminal end to repress E2A mediated transcription may be answered through the conservation of two amino acids, serine and lysine, located at amino acid positions 124 and 125 in the first helix of the HLH domain. This conservation is seen in known transcriptional repressors, such as ceABF -1, MyoR/musculin and capsulin, but is absent in all other identified bHLH proteins.



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