Cell-cycle regulation of the DNA topoisomerase IIα promoter is mediated by proximal CCAAT boxes:: possible involvement of acetylation

Expression of DNA topoisomerase (topo) II alpha is cell-cycle-regulated, with its peak in G(2)/M and its lowest level in G(0)/G(1). In agreement with this expression pattern, we have shown that the topo II alpha gene promoter shows cell-cycle-dependent activity, which is repressed in G(0)/G(1), and activated exclusively in G(2)/M. However, thr promoter sequence reveals no canonical CDE/CHR motifs, repressor elements commonly found in promoters of late S/G(2)-activated genes. Here, we show that at least two of the three proximal inverted CCAAT boxes (ICBs) are responsible for the G(2)/M-specific activation of the topo II alpha. promoter. Using antibody supershift experiments, we identify NF-Y as the ICE-binding transcription factor. However, the expression profile and binding capacity of NF-Y were constant during the cell cycle, suggesting a more global mechanism in topo II alpha promoter regulation. Interestingly, we find that trichostatin A (TSA), a specific histone deacetylase inhibitor, greatly enhances lope IIa promoter activity in an ICE-dependent manner. In addition, the effect of TSA is predominant in G(0)/G(1) and less obvious in G(2)/M. Our data, along with the recent findings that NF-Y associates in vivo with histone acetyltransferases (HATs), strongly suggest a mechanism, in which histone deacetylation plays a crucial role in the G(0)/G(1)-specific repression of the lope II alpha promoter, and NF-Y recruits HATs to the promoter region, thereby stimulating histone acetylation and activating transcription in G(2)/M. (C) 2000 Published by Elsevier Science B.V. All rights reserved.