TOPOISOMERASE I-INHIBITION ENHANCES VITAMIN-D-RESPONSIVE EXPRESSION OF THE RECEPTOR FOR LIPOPOLYSACCHARIDE-BINDING PROTEIN CD-14

Pretreatment (4h) of human HL 60 leukemia cells with the topoisomerase I - inhibitor camptothecin (7-28 x 10(-9) Mol/l single dose) enhanced vitamin D-3 - responsive CD 14 expression (10(-11) - 10(-8) Mol/l vit amin D-3) up to twofold, as measured by fluorescence activated flow cy tometry after 1-3 days. Camptothecin by itself caused marginal effects . Hybridization of total RNA with oligonucleotides (bases 1358-1333 of CD 14 sequence) showed increased steady state levels of the 1,75 kb C D 14 mRNA after 24 h when normalized to beta-actin. The nuclear accumu lation of [H-3]-vitamin D-3/receptor complexes (VDR) in a nuclear tran slocation assay was significantly enhanced (by 3 h) in the presence of camptothecin. We conclude that inhibition of topoisomerase I enhances vitamin D-3-stimulated CD 14 expression. Topoisomerase I might either be a negatively active transcription factor itself or maintenance of DNA-bending, local supercoiling and accessibility of responsive elemen ts might lead to reduction of VDR turnover and produce a stimulatory e ffect on vitamin D-3 - responsive transcription. (C) 1994 Academic Pre ss, Inc.