Abstract
The small nuclear C(3)HC(4) finger protein (SNURF), RNF4, acts as transcriptional coactivator for both steroid-dependent and -independent promoters such as those driven by androgen response elements and GC boxes, respectively. However, SNURF does not possess intrinsic transcription activation function, and the precise molecular mechanism of its action is unknown. We have studied 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. SNURF interacts efficiently with both supercoiled circular and four-way junction DNA, and importantly, it also recognizes nucleosomes. An intact RING structure of SNURF is not mandatory for DNA binding, whereas mutations of specific positively charged residues in the N terminus (amino acids 8-11) abolish DNA binding. Interestingly, the ability of SNURF to interact with DNA is associated with its capability to enhance transcription from promoters containing GC box elements. Because SNURF can interact with both DNA and protein (transcription) factors, it may promote assembly of nucleoprotein structures.
Highlights
RING1 finger is a motif of conserved cysteines and histidines that coordinate two zinc atoms in a “cross-brace” system, a ligation scheme distinct from those of the classical zinc fingers [1, 2]
small nuclear C3HC4 finger protein (SNURF) interacts with androgen receptor (AR) via its N-terminal region, whereas the RING finger plays a key role in the binding to promoter specificity protein 1 (Sp1) [16]
To examine whether SNURF and Sp1 can bind at the same time to the 232-bp rat p75 neurotrophin receptor promoter fragment, the 32P-labeled DNA was incubated with purified Sp1 alone or together with increasing concentrations of GSTSNURF, and the DNA-protein complexes were separated by Electrophoretic Mobility Shift Assay (EMSA)
Summary
RING1 (really interesting new gene) finger is a motif of conserved cysteines and histidines that coordinate two zinc atoms in a “cross-brace” system, a ligation scheme distinct from those of the classical zinc fingers [1, 2]. SNURF interacts with AR via its N-terminal region, whereas the RING finger plays a key role in the binding to promoter specificity protein 1 (Sp1) [16].
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