DUAL EFFECT OF 1-ALPHA,25-DIHYDROXYVITAMIN D-3 ON HSP28 AND PKC-BETA GENE-EXPRESSION IN PHORBOL ESTER-RESISTANT HUMAN MYELOID HL-525 LEUKEMIC-CELLS

We investigated the effect of 1 alpha-25-dihydroxyvitamin D-3 [1,25-(O H)(2)D-3] on the expression of the 28-kDa heat shock protein gene (hsp 28) and the protein kinase C beta gene (PKC beta) in the human myeloid HL-60 leukemic cell variant HL-525, which is resistant to phorbol est er-induced macrophage differentiation. Northern and western blot analy sis showed little or no hsp28 gene expression in the HL-60 cell varian t, HL-205, which is susceptible to such differentiation, while a relat ively high basal level of hsp28 gene expression was observed in the HL -525 cells. However, both cell lines demonstrated heat shock-induced e xpression of this gene. During treatment with 50-300 nM 1,25-(OH)(2)D- 3, a marked reduction of hsp28 gene expression along with an induction of PKC beta gene expression was observed in HL-525 cells. A gel mobil ity-shift assay demonstrated that the 1,25-(OH)(2)D-3-induced alterati on of hsp28 gene expression was associated with decreased binding acti vity to the vitamin D-3 receptor-vitamin D-3 response element (VDR-VDR E), whereas binding to the heat shock transcription factor-heat shock element (HSF-HSE) was not altered. Our results suggest that the dual e ffect of 1,25-(OH)(2)D-3 on hsp28 and PKC beta gene expression is due to the different sequence composition of the vitamin D response elemen t in the promoter region as well as an accessory factor for each gene or that 1,25-(OH)(2)D-3 increases PKC beta gene expression, which, in turn, negatively regulates the expression of the hsp28 gene or vice ve rsa.