GENE STRUCTURE, PROMOTER ACTIVITY, AND CHROMOSOMAL LOCATION OF THE DR-NM23 GENE, A RELATED MEMBER OF THE NM23 GENE FAMILY

DR-nm23 cDNA was cloned recently by differential screening of a cDNA l ibrary derived from chronic myelogenous leukemia-blast crisis primary cells, It is highly homologous to the putative metastasis suppressor n m23-H1 gene and the closely related nm23-H2 gene, When overexpressed i n the myeloid precursor 32Dcl3 cell line, it inhibited granulocyte col ony-stimulating factor-stimulated granulocytic differentiation and ind uced apoptosis, We have now found that the expression of DR-nm23 is no t restricted to hematopoietic cells but is also detected in an array o f solid tumor cell lines, including carcinoma of the breast, colon, an d prostate, as well as the glioblastoma cell line T98G, We have also i solated both the gene and its 5'-flanking region and found that DR-nm2 3 localizes on chromosome 16q13, The gene consists of six exons and fi ve introns, When fused in-frame to the nucleotide sequence for the gre en fluorescent protein and transfected in SAOS-2 cells, it generates a protein of the predicted size that localizes to the cytoplasm, The 5' -flanking region of DR-nm23 does not contain a canonical TATA box or a CAAT box, but it is G+C rich and contains two binding sites for the d evelopmentally regulated transcription factor activator protein 2 (AP- 2). Transient expression assays of DR-nm23 promoter-chloramphenicol ac etyltransferase constructs demonstrated that the segment from nucleoti des -1028 to +123 has the highest activity in hematopoietic K562 cells and in TK-ts13 hamster fibroblasts, Moreover, AP-2 induced a 3-fold t ransactivation of the DR-nm23 5'-flanking segment from nucleotides -16 76 to +123 and interacted specifically with oligomers containing putat ive AP-2 binding sites (-936 to -909, and -548 to -519) as indicated b y electrophoretic mobility shift assay, Furthermore, nuclear run-on as says from high and low DR-nmZ3-expressing cells (K562 and CCRF-CEM, re spectively) revealed similar transcription rates, Therefore, the regul ation of the DR-nm23 gene expression might involve other mechanisms oc curring at posttranscriptional and/or translational levels.