Gain of function of mutant p53: The mutant p53/NF-Y protein complex reveals an aberrant transcriptional mechanism of cell cycle regulation

Cancer Cell, Volume 10, Issue 3, 1 September 2006, Pages 191-202
Silvia Di Agostino, Sabrina Strano, Velia Emiliozzi, Valentina Zerbini, Marcella Mottolese, Ada Sacchi, Giovanni Blandino and Giulia Piaggio

Summary

• This article investigates the mechanistic aspects of mutant p53 gain of function in response to DNA damage. We show that mutant forms of p53 protein interact with NF-Y.
  
• The expression of cyclin A, cyclin B1, cdk1, and cdc25C, as well as the cdk1-associated kinase activities, is upregulated after DNA damage, provoking a mutant p53/NF-Y-dependent increase in DNA synthesis.
  
• Mutant p53 binds NF-Y target promoters and, upon DNA damage, recruits p300, leading to histone acetylation. The recruitment of mutant p53 to the CCAAT sites is severely impaired upon abrogation of NF-YA expression.
  
• Endogenous NF-Y, mutant p53, and p300 proteins form a triple complex upon DNA damage. We demonstrate that aberrant transcriptional regulation underlies the ability of mutant p53 proteins to act as oncogenic factors.

• NF-Y is an ubiquitous heteromeric CCAAT-binding protein composed of three subunits, NF-YA, NF-YB, NF-YC, all necessary for DNA-binding.

• NF-Y sequences are available from several species: the NF-YA gene is cloned from man, rat, mouse, S. pombe, Brassica napus, Schistosoma mansoni and sea urchin (38-41); NF-YB from Kluyveromyces lactis, Aspergillus nidulans, Zea mais, lamprey, Xenopus, and chicken.

• Each of the three subunits displays highly conserved domains in all species. The NF-YA homology domain can be sharply divided into subunit-association and DNA-contacting subdomains. NF-YB and NF-YC tight association is a prerequisite for NF-YA binding and sequence-specific DNA interactions.

• Both NF-YB and NF-YC conserved domains contain putative histone fold motifs. This motif, common to all core histones, is composed of three a-helices separated by short loops/strand regions. NF-YA and NF-YC contain activation domains rich in Glutamines and hydrophobic residues.