Identification of nucleolin as a glucocorticoid receptor interacting protein

The glucocorticoid receptor (GR) is a ligand-induced transcription factor w hich modulates the transcriptional activity of target genes. Full transcrip tional activity of GR is achieved with the help of accessory proteins that are able to interact with GR. We have identified a 95-kDa protein by a blot ting technique which utilizes a radioactively labeled DNA-bound GR to detec t proteins that bind to this complex, Biochemical purification of this prot ein followed by protein microsequencing resulted in the identification of h uman nucleolin, In addition we could show that a GR-deletion mutant localiz es to the nucleolus, where nucleolin is one of the most abundant proteins. The binding of nucleolin to this deletion mutant was demonstrated by GST-pu ll-down experiments. We suggest a biological role of nucleolin in binding o f GR in the nucleolus. (C) 2001 Academic Press.