XENOPUS NF-Y PRE-SETS CHROMATIN TO POTENTIATE P300 AND ACETYLATION-RESPONSIVE TRANSCRIPTION FROM THE XENOPUS HSP70 PROMOTER IN-VIVO

We identify Xenopus NF-Y as a key regulator of acetylation responsiven ess for the Xenopus hsp70 promoter within chromatin assembled in Xenop us oocyte nuclei. Y-box sequences are required for the assembly of DNa se I-hypersensitive sites in the hsp70 promoter, and for transcription al activation both by inhibitors of histone deacetylase and by the p30 0 acetyltransferase. The viral oncoprotein E1A interferes with both of these activation steps. We clone Xenopus NF-YA, NF-YB and NF-YC and e stablish that NF-Y is the predominant Y-box-binding protein in Xenopus oocyte nuclei. NF-Y interacts with p300 in viva and is itself a targe t for acetylation by p300. Transcription from the hsp70 promoter in ch romatin can be enhanced further by heat shock factor We suggest two st eps in chromatin modification at the Xenopus hsp70 promoter: first the binding of NF-Y to the Y-boxes to preset chromatin and second the rec ruitment of p300 to modulate transcriptional activity.