Activation of the AP-1 transcription factor by arabinofuranosylcytosine in myeloid leukemia cells.
Previous studies have shown that 1-beta-D-arabinofuranosylcytosine (ara-C) induces transcription of the c-jun immediate early response gene in human myeloid leukemia cells. The present work has examined the mechanisms responsible for this effect. Deleted forms of the c-jun promoter were linked to the chloramphenicol acetyltransferase (CAT) gene and transfected into KG-1 cells. The results demonstrate that ara-C-induced c-jun transcription is mediated by an element between positions -74 and -20 upstream to the start site. Electrophoretic mobility shift assays with the fragment f(-74/-20) showed an increase in binding with nuclear proteins from ara-C-treated cells as compared with untreated cells. Competition with an oligonucleotide containing the AP-1 consensus sequence indicated that ara-C stimulates binding of nuclear proteins at the AP-1 site in the c-jun promoter. These findings were confirmed in other gel shift studies with the collagenase enhancer AP-1 consensus sequence and with a DNA fragment containing an altered AP-1 site. The binding of JUN/AP-1 was maximal at 1 hour of ara-C treatment and decreased to baseline levels at 12 hours. The finding that ara-C induces AP-1 binding in the absence of protein synthesis indicated that this agent activates already synthesized JUN/AP-1. To confirm these findings, the AP-1 consensus sequence was introduced 5' to the heterologous SV40 promoter. The results show that AP-1 enhances SV40 promoter activity in ara-C-treated cells. Taken together, these findings indicate that: (1) enhancement of JUN/AP-1 activity in ara-C-treated cells involves a posttranslational modification of JUN/AP-1; and (2) binding of activated JUN/AP-1 to the AP-1 site in the c-jun promoter confers ara-C inducibility of this gene.
Brach
M A
MA
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Boston, MA 02115.
Herrmann
F
F
Kufe
D W
DW
D001483:Base Sequence; D003561:Cytarabine / Q000494:pharmacology*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D007951:Leukemia, Myeloid / Q000235:genetics*; D003012:Microbial Collagenase / Q000235:genetics; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics* / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D009841:Oligonucleotides; D016755:Proto-Oncogene Proteins c-jun; D003561:Cytarabine; D003012:Microbial Collagenase