Modulation of topoisomerase IIα expression by a DNA sequence-specific polyamide

Abstract

Topoisomerase IIα (topo IIα) is an important target for several chemotherapeutic agents, including etoposide and doxorubicin. Confluent cells express low levels of topo IIα and are resistant to etoposide treatment. Repression of transcription in confluent cells is mediated by binding of the transcription factor NF-Y to inverted CCAAT motifs within the topo IIα promoter. To block the repressive binding of NF-Y, a polyamide (JH-37) was designed to bind to the flanking regions of selected CCAAT sites within the topo IIα promoter. Electrophoretic mobility shift assays and DNase I footprinting assays showed occupancy of the inverted CCAAT sites by JH-37. Chromatin immunoprecipitation assays confirmed in vivo inhibition of NF-Y binding to the topo IIα promoter. Following incubation of confluent NIH3T3 cells with JH-37, increased expression of topo IIα mRNA and protein was detectable. This correlated both with increased DNA double-strand breaks as shown by comet assay and decreased cell viability following exposure to etoposide. Polyamides can modulate gene expression and chemosensitivity of cancer cells. Copyright © 2007 American Association for Cancer Research.