Vol. 63, Issue 2, 359-367, February 2003

Nuclear Factor-Y Binding to the Topoisomerase II Promoter Is Inhibited by Both the p53 Tumor Suppressor and Anticancer Drugs

Ashish A. Joshi,¹ Zhong Wu,² Robin F. Reed, and D. Parker Suttle

Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee (A.A.J., Z.W., R.F.R., D.P.S.); Research Service, Veterans Affairs Medical Center, Memphis, Tennessee (D.P.S.)

Expression of the human DNA topoisomerase II (topo II) gene is positively regulated by the binding of the nuclear factor Y (NF-Y) transcription factor to four of five inverted CCAAT boxes (ICBs) located in its promoter. We have demonstrated previously that expression of the p53 tumor suppressor inhibits human topo II promoter activity in murine (10)1 cells. In this report, we demonstrate that the inhibition of topo II gene expression by wild-type p53 correlates with the decreased binding of the transcription factor NF-Y to the first four ICBs of the topo II promoter. The expression of mutant p53 does not affect the binding of NF-Y. In NIH3T3 cells, we show that topo II-targeted drugs inhibit the binding of NF-Y to ICB sites in the topo II promoter. This effect is seen not only with drugs that result in DNA strand breaks but also with drugs that inhibit the catalytic activity of topo II, and even with the mitotic spindle inhibitor, vinblastine. Further experiments with p53-null (10)1 cells treated with these same drugs also demonstrate decreased NF-Y binding to the topo II ICBs. The data presented points to the existence of both p53-dependent and -independent mechanisms for regulating NF-Y binding to ICBs in the topo II promoter and thus the modulation of topo II gene expression.