Dominant negative analogs of NF-YA.

NF-Y is a highly conserved heteromeric CCAAT-binding transcription factor involved in the function of several promoters. The NF-YA subunit contains a domain of high homology to yeast HAP2, which we show to be necessary and sufficient to mediate interactions with the NF-YB subunit and with DNA. Using protein affinity columns derivatized with amino acid substitution mutants, we further dissect this region into two functionally separable subdomains. The subunit association function resides in a 21-amino acid stretch, which is almost perfectly conserved among different species, while interaction with DNA resides in another short segment. We also show that DNA-binding mutants act as dominant repressors of NF-Y-DNA complex formation and of NF-Y-dependent transcription.