Protein-Protein Interaction Between the Short and Long Form of Grg Family of Co-Repressors

The Grg family of corepressor proteins lacks DNA-binding domain and these are recruited to the promoter region by interacting with DNA-binding transcription factors. Recruitment to the promoter by DNA-binding transcriptional factors results in transcriptional repression. There are five member of Grg proteins namely Grg1-5. Grg1-4 are the long forms and Grg5 is the short form of Grg family of corepressor. It has been reported that Grg proteins make tetramers to mediate the repression. In a collocatiozation assay, the full length myc-mGrg3 was transfected in COS7 cells along with mGrg5 and mGrg1∆280 fused with GFP. The colocalization assay indicates that full length myc-mGrg3 interacts with short form mGrg5-GFP by changing the localization pattern of mGrg5-GFP from cytoplasm to nucleus. In addition, we have also shown that Grg proteins interact with each other via N-terminal end, since myc-mGrg3 could not alter the translocation of non nuclear truncated form mGrg1∆280-GFP from cytoplasm into the nucleus. The inability of myc-mGrg3 to translocate mGrg1∆280-GFP indicates that Grg protein interact with each other only via N-terminal end. In conclusion, results we show here suggest that Grg protein interact with each other via N-terminal end and that this interaction alters the localization pattern of interacting Grg proteins.

Keywords: COS7 cells, Grg proteins, Colocalization assay.