Journal
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 390, Issue 1, Pages 21-26Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2009.09.044
Keywords
MYCN; Neuroblastoma; Neuronal differentiation; All-trans-retinoic acid (ATRA); Positive auto-regulation
Categories
Funding
- Ministry of Health, Labor and Welfare
- Ministry of Education, Culture, Sports, Science and Technology, Japan
- Japan Society for the Promotion of Science
- Uehara Memorial Foundation
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MYCN oncogene is one of the most important regulators affecting the prognosis of neuroblastoma and is frequently amplified in the high-risk subsets. Despite its clinical significance, it remains unclear how the MYCN expression is regulated in human neuroblastomas. Here, we found the presence of a positive autoregulatory mechanism of MYCN. Enforced expression of MYCN induced endogenous MYCN mRNA expression in SK-N-AS neuroblastoma cells with a single copy of MYCN gene. Luciferase reporter assay revealed that MYCN protein activates its own promoter activity in a dose-dependent manner and the downstream region relative to the transcription start sites is responsible for the activation. Furthermore, ChIP analysis showed that MYCN is directly recruited onto the intron I region of MYCN gene which contains two putative E-box sites. Intriguingly, in response to all-trans-retinoic acid (ATRA), MYCN was down-regulated in MYCN-amplified SK-N-BE neuroblastoma cells, and the recruitment of MYCN protein onto its own intron I region was reduced in association with an induction of neuronal differentiation. Collectively, our present results suggest that MYCN contributes to its own expression by forming a positive auto-regulatory loop in neuroblastoma cells. (C) 2009 Published by Elsevier Inc.
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