Characterization of the human transcription factor Zhangfei through the analysis of associating proteins and target genes

The human protein Zhangfei (ZF) is a member of the bZIP family of transcription factors and was identified through its association with Host Cell Factor (HCF). The mode of action of ZF in the mammalian cell, along with its biological functions, is presently unclear. This thesis is an investigation into the identity of ZF associating proteins as well as downstream target genes for ZF mediated transcriptional regulation. A yeast two-hybrid assay identified specific regions from α-thalassemia/mental retardation syndrome X-linked factor (ATRX), Ran binding protein RanBPM and p30 that were capable of associating with the ZF bZIP domain in yeast. Two independent biochemical protein-protein interaction assays confirmed an association between the RanBPM C-terminus and ZF. The possible significance of ATRX and RanBPM associations with ZF is discussed. Microarray analysis identified several genes that were differentially regulated in a positive and negative manner in the presence of ZF. This observation suggests that ZF functions as both a transcriptional activator and repressor. A number of the genes differentially expressed in the presence of ZF encode for proteins that regulate cytoskeleton structure. The possibility of ZF serving as an intermediate in signaling cascades mediating cellular cytoskeleton reorganization is discussed.