IDENTIFICATION OF IMMEDIATE-EARLY GENES DURING TPA-INDUCED HUMAN MYELOBLASTIC-LEUKEMIA ML-1 CELL-DIFFERENTIATION

Human myeloblastic ML-1 can be induced to differentiate into monocytes /macrophages by 12-0-tetradecanoylphorbol-13-acetate (TPA). In order t o understand the molecular mechanism regulating ML-1 cell differentiat ion, we focused on the characterization of immediate early genes activ ated by TPA using the mRNA differentiation display polymerase chain re action (DD-PCR) and Northern analyses. A modified procedure, the rever se dot slot, was developed to confirm upregulated genes during the ear ly stages of TPA-induced ML-1 cell differentiation. DNA sequencing ana lyses of 10 subcloned cDNA fragments, selected on the basis of the out come of the reverse dot slot procedure, revealed that eight were deriv ed from distinct genes. Among these clones, one was a novel gene (G07- 5), another (A02-1) was highly homologous to the sequence of a fetal b rain cDNA fragment, and the remaining six corresponded to jun-D rantes , ssat, CD 14, ferritin heavy chain (fhc) and transposons Tn10-like tr anscript, respectively. Although these genes were all upregulated by T PA, the peak time of mRNA expression varied, jun-D, ssat and A02-1 exp ressions were superinduced in the presence of cycloheximide, which ind icates that they belong to the immediate early gene family. On the oth er hand, TPA-induced rantes expression was not superinduced by cyclohe ximide, suggesting a protein synthesis-dependent process. As there are no previous reports of expression of these genes in TPA-induced ML-1 cells, little or no information is available concerning their function in mediating myeloblastic cell differentiation. Thus, this study illu minates new avenues of research for elucidating the function of genes regulating terminal differentiation of myeloid progenitors. (C) 1998 E lsevier Science B.V. All rights reserved.