Genome-wide DNA binding of GBF1 is modulated by its heterodimerizing protein partners, HY5 and HYH

Abstract

In today’s post-genomic era where direct targets of many transcription factors have been identified, it is becoming increasingly evident that transcriptional networks are very complex. Heterodimerization of transcription factors is one of the several methods by which these complex transcriptional networks are formed. By heterodimerization, DNA- binding specificity and affinity, transactivation properties, and ultimately cell physiology might be altered (Naar et al., 2001). The formation of heterodimers has the potential to recognize additional binding sites and increase the range of DNA-binding specificity (Foster et al., 1994). Further, heterodimerization also allows the production of new protein configurations. For example, the protein STF1 from soybean can dimerize with GBF proteins and this dimerization brings together the acidic region from STF1 and the proline-rich region of the GBF proteins into one binding element (Cheong et al., 1998). These results highlight the importance and/or consequences of heterodimerization of transcription factors at particular locus. However, to understand the complex transcriptional networks, it is important to investigate that how heterodimerization affects the whole-genome-wide binding and transcriptional properties of a transcription factor. Here in this study, we have investigated genome-wide DNA binding of bZIP transcription factor GBF1, and analyzed the importance of its heterodimerization with HY5 and HYH for its genome-wide binding. We have found that GBF1 binding sites are enriched within the 1-kb regions upstream to the transcription start sites of target genes. Moreover, the bindings of GBF1 to most of its targets are largely dependent on HY5, while HYH only affects the binding of GBF1 to some specific sites.