Regulated expression of the MRP8 and MRP14 genes in human promyelocytic leukemic HL-60 cell treated with the differentiation-inducing agents mycophenolic acid and 1(alpha),25-dihydroxyvitamin D(sub 3)

摘要

The calcium-binding proteins MRP8 and MEP14 are present in mature monomyelocytic cells and are induced during differentiation. Previous studies have demonstrated that the proteins may mediate the growth arrest in differentiating HL-60 cells. We determined the levels of a protein complex (PC) containing MRP8 and MRP14 and investigated the mechanism by which the genes encoding these proteins are regulated in HL-60 cells treated with the differentiation-inducing agent mycophenorc acid (MPA)While the PC was barely detectable in untreated cells, MPA treatment resulted in elevated levels of the PC which were maximal at 3-4 d, and were found to directly parallel gains in the steady-state levels of MRP8 and MRP14 MRNA. Transcription studies with the use of nuclear run-on experiments revealed increased transcription initiation at the MRP8 and MRP14 promoters after MPA treatment. 1(alpha),25-Dihydroxyvitamin D(sub 3), which induces HL-60 cell differentiation by another mechanism, was also found to increase transcription initiation at the MRP8 and MRP14 promoters. Our results suggest that this initiation is the major control of maturation agent-mediated increases in MRP8 and MRPl4 gene expression, and support a role for the PC in terminal differentiation of human monomyelocytic cells.