cAMP-induced NF-κB (p50/relB) binding to a c-myb intronic enhancer correlates with c-myb up-regulation and inhibition of erythroleukemia cell differentiation

• Published in: Oncogene Vol. 15; no. 15; pp. 1859 - 1870
• Main Authors: SUHASINI, M, REDDY, C. D, REDDY, E. P, DIDONATO, J. A, PILZ, R. B
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 09.10.1997; Nature Publishing Group
• Subjects: Activator protein 1; Biological and medical sciences; c-Fos protein; c-Myb protein; Cell differentiation; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cyclic AMP; Erythroleukemia; Forskolin; Fundamental and applied biological sciences. Psychology; JunB protein; Molecular and cellular biology; NF-κB protein; Proto-oncogenes; RelB protein; Transcription factors; Transfection; Up-regulation; Erythroleukemia; Induction; Rodentia; Cyclic AMP; Molecular interaction; Malignant hemopathy; Cell differentiation; Gene expression; Cell transformation; Myeloproliferative syndrome; Vertebrata; Regulation(control); Enhancer sequence; Mammalia; Mouse; C-Onc gene; Regulatory sequence; Molecular complex; Inhibition
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/sj.onc.1201530

During hexamethylene bisactamide (HMBA)-induced differentiation of murine erythroleukemia (MEL) cells erythroid genes are transcriptionally activated while c-myb and several other nuclear proto-oncogenes are down-regulated. Differentiation is inhibited by cAMP analogues and the adenyl cyclase-stimulating agent forskolin. We found that these drugs prevented the late down-regulation of c-myb which is known to be critical for MEL cell differentiation. Since the increase in c-myb mRNA levels was due to increased mRNA transcription, we examined the transcription factors NF-κB and AP-1 which have been implicated in the regulation of c-myb expression. Binding of MEL cell nuclear proteins to a NF-κB recognition sequence in c-myb intron I was strongly induced by 8-Br-cAMP or forskolin; induction was delayed and correlated with the up-regulation of c-myb. The cAMP-induced NF-κB complex contained p50 and RelB; in co-transfection assays, p50 and RelB transactivated a reporter construct containing the c-myb intronic NF-κB site upstream of a minimal promoter. 8-Br-cAMP and forskolin also increased the DNA binding activity of AP-1 complexes containing JunB, JunD and c-Fos in MEL cells which could cooperate with NF-κB. We conclude that inhibition of MEL cell differentiation by pharmacological doses of cAMP can be explained by the up-regulation of c-myb which is mediated, at least in part, by NF-κB p50/RelB heterodimers.