Direct recruitment of N-myc to target gene promoters

Susanna M. Mac, Caroline A. D'Cunha, Peggy J. Farnham

Research output: Contribution to journalArticle

Abstract

The N-myc gene is amplified in 20-25% of human neuroblastomas, and this amplification serves as a poor prognostic factor. However, few genes have been determined to be direct targets of N-myc. Our current studies focused on identifying N-myc target genes, especially those affected in cells such as neuroblastomas that have high levels of N-myc protein. To pursue this goal, we performed differential expression screens with cell-culture systems containing high versus low levels of N-myc. The design of our experiments was such that we should identify genes both upregulated and downregulated by N-myc. Accordingly, we identified 22 genes upregulated by N-myc and one gene downregulated by N-myc. However, only five of these genes responded to increased N-myc levels in more than one system. Further analysis of the regulation of these genes required determining whether they were direct or indirect targets of N-myc. Therefore, we used a formaldehyde crosslinking and immunoprecipitation procedure to determine whether N-myc was bound to the promoters of these putative target genes in living cells. We found that low levels of N-myc were bound to the promoters of the telomerase and prothymosin genes in neuroblastoma cells having low amounts of N-myc but that the amounts of N-myc bound to these promoters greatly increased with overexpression of N-myc. However, the amount of max bound to the promoters was high before and after induction of N-myc. Therefore, our studies suggest that N-myc competes with other max partners for binding to target promoters. Our use of the chromatin immunoprecipitation assay suggests a molecular explanation for the consequences of amplification of the N-myc gene in neuroblastomas. (C) 2000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)76-86
Number of pages11
JournalMolecular Carcinogenesis
Volume29
Issue number2
DOIs
StatePublished - 2000
Externally publishedYes

Fingerprint

myc Genes
Neuroblastoma
Genes
Down-Regulation
Chromatin Immunoprecipitation
Telomerase
Immunoprecipitation
Formaldehyde
Cell Culture Techniques

Keywords

  • Chromatin
  • Formaldehyde crosslinking
  • Neuroblastoma
  • Nuclear oncogene
  • Transcription

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research

Cite this

Direct recruitment of N-myc to target gene promoters. / Mac, Susanna M.; D'Cunha, Caroline A.; Farnham, Peggy J.

In: Molecular Carcinogenesis, Vol. 29, No. 2, 2000, p. 76-86.

Research output: Contribution to journalArticle

Mac, Susanna M. ; D'Cunha, Caroline A. ; Farnham, Peggy J. / Direct recruitment of N-myc to target gene promoters. In: Molecular Carcinogenesis. 2000 ; Vol. 29, No. 2. pp. 76-86.
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AB - The N-myc gene is amplified in 20-25% of human neuroblastomas, and this amplification serves as a poor prognostic factor. However, few genes have been determined to be direct targets of N-myc. Our current studies focused on identifying N-myc target genes, especially those affected in cells such as neuroblastomas that have high levels of N-myc protein. To pursue this goal, we performed differential expression screens with cell-culture systems containing high versus low levels of N-myc. The design of our experiments was such that we should identify genes both upregulated and downregulated by N-myc. Accordingly, we identified 22 genes upregulated by N-myc and one gene downregulated by N-myc. However, only five of these genes responded to increased N-myc levels in more than one system. Further analysis of the regulation of these genes required determining whether they were direct or indirect targets of N-myc. Therefore, we used a formaldehyde crosslinking and immunoprecipitation procedure to determine whether N-myc was bound to the promoters of these putative target genes in living cells. We found that low levels of N-myc were bound to the promoters of the telomerase and prothymosin genes in neuroblastoma cells having low amounts of N-myc but that the amounts of N-myc bound to these promoters greatly increased with overexpression of N-myc. However, the amount of max bound to the promoters was high before and after induction of N-myc. Therefore, our studies suggest that N-myc competes with other max partners for binding to target promoters. Our use of the chromatin immunoprecipitation assay suggests a molecular explanation for the consequences of amplification of the N-myc gene in neuroblastomas. (C) 2000 Wiley-Liss, Inc.

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