Genes Dev 1997 Mar 1;11(5):558-570
Department of Biological Sciences, Columbia University, New York,
New York 10027, USA.
p53 can be isolated from cells in a form that is inert for binding
to DNA but that can be stimulated dramatically by phosphorylation,
antibody binding, or short single strands of DNA. This suggests that
upon genotoxic stress, cells can convert latent p53 to one that is
active for DNA binding. Surprisingly, we observed that latent p53 is
as effective in activating transcription in vitro as is active p53.
We found that HeLa nuclear extracts can stimulate DNA binding by
latent p53 and have purified from them a p53-stimulating protein that
we have determined to be the product of the Ref-1 gene.
Interestingly, Ref-1 is a dual function protein that can both
regulate the redox state of a number of proteins and function as a
DNA repair (A/P) endonuclease. We observed that oxidized forms of
full-length and carboxy-terminally truncated p53 (p53 delta30), which
are inactive for DNA binding, are both stimulated by the Ref-1
protein. However, in the presence of reducing agent, Ref-1 is an
extremely potent stimulator of full-length p53 but not p53 delta30.
These and additional data indicate that Ref-1 protein stimulates p53
by both redox-dependent and -independent means and imply a key role
for it in p53 regulation. Importantly, we have also determined that
Ref-1 can stimulate p53 transactivation in vivo. This is the first
example of a noncovalent protein modifier of p53 function identified