DOMINANT-NEGATIVE ANALOGS OF NF-YA

NF-Y is a highly conserved heteromeric CCAAT-binding transcription fac tor involved in the function of several promoters. The NF-YA subunit c ontains a domain of high homology to yeast HAP2, which we show to be n ecessary and sufficient to mediate interactions with the NF-YB subunit and with DNA. Using protein affinity columns derivatized with amino a cid substitution mutants, we further dissect this region into two func tionally separable subdomains. The subunit association function reside s in a 21-amino acid stretch, which is almost perfectly conserved amon g different species, while interaction with DNA resides in another sho rt segment. We also show that DNA-binding mutants act as dominant repr essors of NF-Y.DNA complex formation and of NF-Y-dependent transcripti on.