Activation domains of L-Myc and c-Myc determine their transforming potencies in rat embryo cells

John Barrett, Michael J. Birrer, Gregory J. Kato, Hirotoshi Dosaka-Akita, Chi V. Dang

Research output: Contribution to journalArticle

Abstract

Members of the Myc family of proteins share a number of protein motifs that are found in regulators of gene transcription. Conserved stretches of amino acids found in the N-terminal transcriptional activation domain of c-Myc are required for cotransforming activity. Most of the Myc proteins contain the basic helix-loop-helix zipper (bHLH-Zip) DNA-binding motif which is also required for the cotransforming activity of c-Myc. L-Myc, the product of a myc family gene that is highly amplified in many human lung carcinomas, was found to cotransform primary rat embryo cells with an activated ras gene. However, L-Myc cotransforming activity was only 1 to 10% of that of c-Myc (M. J. Birrer, S. Segal, J. S. DeGreve, F. Kaye, E. A. Sausville, and J. D. Minna, Mol. Cell. Biol. 8:2668-2673, 1988). We sought to determine whether functional differences between c-Myc and L-Myc in either the N-terminal or the C-terminal domain could account for the relatively diminished L-Myc cotransforming activity. Although the N-terminal domain of L-Myc could activate transcription when fused to the yeast GAL4 DNA-binding domain, the activity was only 5% of that of a comparable c-Myc domain. We next determined that the interaction of the C-terminal bHLH-Zip region of L-Myc or c-Myc with that of a Myc partner protein, Max, was equivalent in transfected cells, A Max expression vector was found to augment the cotransforming activity of L-Myc as well as that of c-Myc. In addition, a bacterially synthesized DNA-binding domain of L-Myc, like that of c-Myc, heterodimerizes with purified Max protein to bind the core DNA sequence CACGTG. To determine the region of L-Myc responsible for its relatively diminished cotransforming activity, we constructed chimeras containing exons 2 (constituting activation domains) and 3 (constituting DNA-binding domains) of c-Myc fused to those of L-Myc. The cotransforming potencies of these chimeras were compared with those of full-length L-Myc or c-Myc in rat embryo cells. The relative cotransforming activities suggest that the potencies of the activation domains determine the cotransforming efficiencies for c-Myc and L-Myc. This correlation supports the hypothesis that the Myc proteins function in neoplastic cotransformation as transcription factors.

Original languageEnglish (US)
Pages (from-to)3130-3137
Number of pages8
JournalMolecular and Cellular Biology
Volume12
Issue number7
StatePublished - Jul 1992

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Embryonic Structures
DNA
Amino Acid Motifs
Nucleotide Motifs
Proteins
myc Genes
ras Genes
Regulator Genes
Transcriptional Activation
Exons
Transcription Factors
Yeasts
Carcinoma
Amino Acids
Lung
Myc associated factor X

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

Barrett, J., Birrer, M. J., Kato, G. J., Dosaka-Akita, H., & Dang, C. V. (1992). Activation domains of L-Myc and c-Myc determine their transforming potencies in rat embryo cells. Molecular and Cellular Biology, 12(7), 3130-3137.

Activation domains of L-Myc and c-Myc determine their transforming potencies in rat embryo cells. / Barrett, John; Birrer, Michael J.; Kato, Gregory J.; Dosaka-Akita, Hirotoshi; Dang, Chi V.

In: Molecular and Cellular Biology, Vol. 12, No. 7, 07.1992, p. 3130-3137.

Research output: Contribution to journalArticle

Barrett, J, Birrer, MJ, Kato, GJ, Dosaka-Akita, H & Dang, CV 1992, 'Activation domains of L-Myc and c-Myc determine their transforming potencies in rat embryo cells', Molecular and Cellular Biology, vol. 12, no. 7, pp. 3130-3137.
Barrett J, Birrer MJ, Kato GJ, Dosaka-Akita H, Dang CV. Activation domains of L-Myc and c-Myc determine their transforming potencies in rat embryo cells. Molecular and Cellular Biology. 1992 Jul;12(7):3130-3137.
Barrett, John ; Birrer, Michael J. ; Kato, Gregory J. ; Dosaka-Akita, Hirotoshi ; Dang, Chi V. / Activation domains of L-Myc and c-Myc determine their transforming potencies in rat embryo cells. In: Molecular and Cellular Biology. 1992 ; Vol. 12, No. 7. pp. 3130-3137.
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