Transcription factors (TFs) recognise specific genome regions and form a complex that controls chromatin and gene expression. TFs contain two separable components: a DNA binding domain (DBD) and a functional domain (FD). It was historically believed that the DBD was the only region that determined the genomic localisation of transcription factors. However, evidence has emerged that the FD can also play a role in determining the genomic localisation of transcription factors. Based on extensive preliminary data, we hypothesise that binding to histone marks by transcription factor FDs may be a general mechanism by which FDs can direct the genomic localisation of transcription factors.
We aim to explore the impact of histone reader recruitment on the genomic localisation of transcription factors, by binding histone reader domains to a model artificial zinc finger (AZF) protein that targets the vascular endothelial growth factor-A gene promoter. We have fused histone reader domains to the AZF to investigate whether these domains are sufficient to direct the AZF to new target genes. We have generated stable HEK293 cell lines that express these fusion proteins. We also confirmed the successful binding of these fusion proteins to the AZF recognition motif in vitro with electrophoretic mobility shift assay (EMSA). We have recently performed chromatin immunoprecipitation sequencing to test whether the fused histone readers alter the genomic localisation of the AZF. If this is indeed the case, it would suggest that the recruitment of histone readers by transcription factor FDs is an important determinant of genomic localisation and target gene selection. This knowledge could be applied to harness histone readers to design improved artificial transcription factors that can reprogram gene expression and control cell differentiation.