hnRNP U interacts with the c-Myc-Max complex on the E-box promoter region inducing the ornithine decarboxylase gene.
The promoter of the ornithine decarboxylase (ODC) gene contains two E-boxes, which are critical sites for transcriptional activation by the binding of c-Myc-Max heterodimers. We have identified heterogeneous nuclear ribonuclear protein U (hnRNP U) as a component of the complex formed on the E-box-containing promoter region of the ODC gene by using DNA-affinity chromatography, immunoprecipitation and chromatin immunoprecipitation assays. The N-terminal domain of hnRNP U was responsible for the association with c-Myc-Max complex. Down-regulation of hnRNP U with RNA interference blocked the induction of the ODC gene and cell growth by serum stimulation, suggesting that hnRNP U is a coactivator of the c-Myc-Max complex and essential for cell proliferation. Electrophoretic mobility-shift assays revealed that the segment between the two E-boxes in the promoter is the primary binding site of hnRNP U. The putative binding sequence was narrowed-down to a 13-nucleotide segment by comparing the sequence between the E-boxes with the binding sites of hnRNP U, which were recently identified in the promoter of Bmal1, a core component of the circadian molecular oscillator. These findings increase our knowledge of how the c-Myc-Max complex exerts its transcriptional regulatory role and suggest that hnRNP U may be a coactivator of this transcriptional activator complex.
Matsuoka
Yoichiro
Y
Second Department of Pathology, Kansai Medical University, Osaka 570-8506, Japan. matsuoyo@takii.kmu.ac.jp
Uehara
Norihisa
N
Tsubura
Airo
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000502:physiology*; D024721:E-Box Elements; D034722:Heterogeneous-Nuclear Ribonucleoprotein U / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D009955:Ornithine Decarboxylase / Q000235:genetics*; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D015533:Transcriptional Activation
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; C489428:Myc protein, mouse; D016271:Proto-Oncogene Proteins c-myc; C068422:Max protein, mouse; D009955:Ornithine Decarboxylase