Regulation of c-myc transcription by NDPK in human neuroblastoma cells

• Main Authors: Yi-wei Huang, 黃苡瑋
• Other Authors: Christina Ling Chang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/91294289547087644158

碩士 === 國立成功大學 === 分子醫學研究所 === 96 === Nucleoside diphosphate kinase (NDPK)-A behaves as a metastasis promoter in neuroblastoma, which is a common childhood tumor arising from the neural crest. Overexpression or S120G mutation of NDPK-A have been detected in patients with advanced stages of neuroblastoma. Such NDPK-A alterations abrogate neuronal differentiation and enhance cell invasiveness in vitro, while promoting neuroblastoma metastasis in animals. Currently it is unclear how NDPK-A is involved in tumor metastasis. However, it is known that c-myc plays an essential role in neural crest development. NDPK-A shares 88% identity with NDPK-B and the latter participates in the regulation of c-myc transcription. In this study, I therefore examined the individual and collaborative effects of NDPK-A and NDPK-B on c-myc transcriptional regulation in the human neuroblastoma NB69 cell model. Using c-myc promoter deletion mutants and the CAT assay, I found that negatively regulatory cis-elements were present in nuclease hypersensitive element (NHE) III1 and II regions, whereas positively regulatory cis-elements localized to upstream of NHE II2. Although NDPK-A or NDPK-AS120G did not significantly affect c-myc promoter activity, either protein inhibited c-myc transcriptional derepression via NHE III1 and NHE II in NB69-derived transient and stable transfectants. On the other hand, NDPK-B significantly activated the c-myc promoter activity likely via cis-elements other than NHE III1. However, NDPK-B activated c-myc transcription was abrogated by NDPK-A or NDPK-AS120G in NB69 cells. My current findings provide the first evidence showing that NDPK-A plays a different role from NDPK-B in c-myc transcriptional regulation. My results suggest that NDPK-A may modulate c-myc transcription via NHE III1 and yet-to-be identified cis-elements in NHE II in a non-conventional fashion in NB69 cells. It is possible that overexpression or S120G mutation of NDPK-A deregulates c-myc transcription, which in turn may affect neural crest development and lead to metastatic neuroblastoma.