The RING finger protein SNURF is a bifunctional protein possessing DNA binding activity

The small nuclear C3HC4 finger protein (SNURF), RNF4, acts as transcription al coactivator for both steroid-dependent and -independent promoters such a s those driven by androgen response elements and GC boxes, respectively. Ho wever, SNURF does not possess intrinsic transcription activation function, and the precise molecular mechanism of its action is unknown, We have studi ed herein the interaction of SNURF with DNA in vitro, SNURF binds to linear double-stranded DNA with no apparent sequence specificity in a cooperative fashion that is highly dependent on the length of the DNA fragment used. S NURF interacts efficiently with both supercoiled circular and four-way junc tion DNA, and importantly, it also recognizes nucleosomes. An intact RING s tructure of SNURF is not mandatory for DNA binding, whereas mutations of sp ecific positively charged residues in the N terminus (amino acids 8-11) abo lish DNA binding. Interestingly, the ability of SNURF to interact with DNA is associated with its capability to enhance transcription from promoters c ontaining GC box elements. Because SNURF can interact with both DNA and pro tein (transcription) factors, it may promote assembly of nucleoprotein stru ctures.