Direct regulation of the minichromosome maintenance complex by MYCN in neuroblastoma Arjen Koppen a , Rachida Ait-Aissa a , Jan Koster a , Peter G. van Sluis a , Ingrid Øra a,c , Huib N. Caron a,b , Richard Volckmann a , Rogier Versteeg a , Linda J. Valentijn a, * a Department of Human Genetics, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands b Department of Paediatric Oncology and Haematology, Emma Kinder Ziekenhuis, Academic Medical Center, Amsterdam, The Netherlands c Department of Paediatric Oncology and Haematology, Lund University Hospital, 22185 Lund, Sweden ARTICLE INFO Article history: Received 21 May 2007 Accepted 18 July 2007 Available online 10 September 2007 Keywords: DNA replication MCM Neuroblastoma MYCN ABSTRACT The c-Myc and MYCN oncogenes strongly induce cell proliferation. Although a limited ser- ies of cell cycle genes were found to be induced by the myc transcription factors, it is still unclear how they mediate the proliferative phenotype. We therefore analysed a neuroblas- toma cell line with inducible MYCN expression. We found that all members of the minichro- mosome maintenance complex (MCM2–7) and MCM8 and MCM10 were up-regulated by MYCN. Expression profiling of 110 neuroblastoma tumours revealed that these genes strongly correlated with MYCN expression in vivo. Extensive chromatin immunoprecipita- tion experiments were performed to investigate whether the MCM genes were primary MYCN targets. MYCN was bound to the proximal promoters of the MCM2 to -8 genes. These data suggest that MYCN stimulates the expression of not only MCM7, which is a well defined MYCN target gene, but also of the complete minichromosome maintenance complex. Ó 2007 Elsevier Ltd. All rights reserved. 1. Introduction Members of the Myc oncogene family are activated in many tumour types and can induce strong changes in the cellular phenotype. They stimulate cell growth, proliferation and invasiveness upon ectopic expression. The Myc oncogene family members, MYC, MYCN and MYCL, are basic-helix– loop–helix-leucine zipper domain containing transcription factors, which activate, together with their dimerization part- ner Max, gene expression of a number of genes in an E-box (CAC(A/G)TG) dependent manner. 1,2 MYCN and c-myc proba- bly have very similar molecular functions. Mice in which the coding sequence of MYC was replaced by that of MYCN devel- oped normally. This indicates that MYCN and c-myc can functionally replace each other and control the same cellular processes. 3 High throughput mRNA profiling studies have identified many genes which are induced upon myc activation, but di- rect regulation by the myc transcription factors was estab- lished for only a limited number of genes. These myc- induced changes in gene expression start to explain the phe- notypic changes known to result from myc activation. The Drosophila MYC gene promotes cell growth and indeed mam- malian c-myc stimulates expression of several genes involved in protein synthesis. 4,5 We observed that MYCN and c-myc stimulate expression of proteins involved in ribosomal RNA processing and ribosome biogenesis. 6 The role of myc onco- genes in cell adhesion and tumour invasion 7–9 is in line with our recent observation that MYCN down-regulates the expression of many genes involved in cell–matrix interactions and in cytoskeleton architecture. 10 Most research has focused on the effect of myc oncogenes on cell proliferation. Indeed a 0959-8049/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ejca.2007.07.024 * Corresponding author: Tel.: +31 205666592; fax: +31 206918626. E-mail address: l.j.valentijn@amc.uva.nl (L.J. Valentijn). EUROPEAN JOURNAL OF CANCER 43 (2007) 2413 – 2422 available at www.sciencedirect.com journal homepage: www.ejconline.com