Nuclear immobilization of DsRed1 tagged proteins: a novel tool for studying DNA-protein interactions?

DsRed1 is a red fluorescent protein that can be used as a fusion partner with other proteins to determine their subcellular localization, similarly to the popular green fluorescent proteins (GFP). Here, we report that fusion of DsRed1 to estrogen receptor alpha (ER alpha) renders the transcription factor immobile within the nucleus. Furthermore, we show that the immobilization is dependent on DNA interaction and that the binding to the DNA can be direct as well as indirect for DsRed to immobilize with its fusion partners. This observation could provide a new tool to be used for the identification of target genes containing low affinity binding sites for several transcription factors including ER alpha. In addition, it could be employed for studies on protein-DNA interactions as well as protein-protein interactions during protein complex formation on chromatin in the event of transcription initiation and regulation.