Myc‐Max heterodimers activate a DEAD box gene and interact with multiple E box‐related sites in vivo

• Published in: The EMBO journal 1996-08, Vol.15 (16), p.4344-4357
• Main Authors: Grandori, C., Mac, J., Siëbelt, F., Ayer, D. E., Eisenman, R. N.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Basic-Leucine Zipper Transcription Factors; Binding Sites; Burkitt Lymphoma - pathology; Cell Differentiation - drug effects; Cells, Cultured; Cycloheximide - pharmacology; Dimerization; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - physiology; Estradiol - pharmacology; Gene Expression Regulation - drug effects; Helix-Loop-Helix Motifs; HL-60 Cells; Humans; Leucine Zippers; Molecular Sequence Data; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Proto-Oncogene Proteins c-myc - chemistry; Proto-Oncogene Proteins c-myc - physiology; Rats; Receptors, Estrogen - genetics; Recombinant Fusion Proteins - metabolism; Regulatory Sequences, Nucleic Acid; RNA Helicases; RNA Nucleotidyltransferases - genetics; RNA Nucleotidyltransferases - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Transcription Factors; Tumor Cells, Cultured
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1996.tb00808.x

The c‐Myc protein is involved in cell proliferation, differentiation and apoptosis though heterodimerization with Max to form a transcriptionally active sequence‐specific DNA binding complex. By means of sequential immunoprecipitation of chromatin using anti‐Max and anti‐Myc antibodies, we have identified a Myc‐regulated gene and genomic sites occupied by Myc‐Max in vivo. Four of 27 sites recovered by this procedure corresponded to the highest affinity ‘canonical’ CACGTG sequence. However, the most common in vivo binding sites belonged to the group of ‘non‐canonical’ E box‐related binding sites previously identified by in vitro selection. Several of the genomic fragments isolated contained transcribed sequences, including one, MrDb, encoding an evolutionarily conserved RNA helicase of the DEAD box family. The corresponding mRNA was induced following activation of a Myc‐estrogen receptor fusion protein (Myc‐ER) in the presence of a protein synthesis inhibitor, consistent with this helicase gene being a direct target of Myc‐Max. In addition, as for c‐Myc, the expression of MrDb is induced upon proliferative stimulation of primary human fibroblasts as well as B cells and down‐regulated during terminal differentiation of HL60 leukemia cells. Our results indicate that Myc‐Max heterodimers interact in vivo with a specific set of E box‐related DNA sequences and that Myc is likely to activate multiple target genes including a highly conserved DEAD box protein. Therefore, Myc may exert its effects on cell behavior through proteins that affect RNA structure and metabolism.