Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein

Elizabeth M. Blackwood, Tracy Gross Lugo, Leo Kretzner, Michael King, Alasdair J. Street, Owen N. Witte, Robert N. Eisenman

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Activation of the c-myc proto-oncogene by chromosomal translocation or proviral insertion frequently results in the separation of the c-myc coding region from its normal regulatory elements. Such rearrangements are often accompanied by loss or mutation of c-myc exon 1 sequences. These genetic alterations do not affect synthesis of the major c-myc protein, p64, which is initiated from the first AUG codon in exon 2. However they can result in mutation or loss of the CUG codon located in exon 1 that normally serves as an alternative translational initiation codon for synthesis of an N- terminally extended form of c-Myc (p67). It has been hypothesized that p67 is a functionally distinct form of c-Myc whose specific loss during c-myc rearrangements confers a selective growth advantage. Here we describe experiments designed to test the functional properties of the two c-Myc protein forms. We introduced mutations within the translational initiation codons of a normal human c-myc cDNA that alter the pattern of Myc protein synthesis (p64 vs. p67). The functions of each of these proteins were experimentally addressed using co-transformation and transcriptional activation assays. Both the p64 and p67 c-Myc proteins were independently able to collaborate with bcr-abl in the transformation of Rat-1 fibroblasts. In addition, both the exon 1- and exon 2-initiated forms of the c-Myc protein stimulated transcription of a Myc/Max-responsive reporter construct to a similar level. Given the apparent absence of functional differences between p64 and p67, we conclude that the basis for c-Myc oncogenic activation lies primarily in the overall deregulation of its expression and not in alterations in the protein. The existence of the CUG translational initiator may reflect a mechanism for the continued synthesis of c-Myc protein under conditions where AUG initiation is inhibited.

Original languageEnglish
Pages (from-to)597-609
Number of pages13
JournalMolecular Biology of the Cell
Volume5
Issue number5
StatePublished - May 1994

Fingerprint

Proto-Oncogene Proteins c-myc
Exons
Initiator Codon
Codon
Mutation
Genetic Translocation
Proteins
myc Genes
Transcriptional Activation
Complementary DNA
Fibroblasts
Growth

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

Blackwood, E. M., Lugo, T. G., Kretzner, L., King, M., Street, A. J., Witte, O. N., & Eisenman, R. N. (1994). Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein. Molecular Biology of the Cell, 5(5), 597-609.

Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein. / Blackwood, Elizabeth M.; Lugo, Tracy Gross; Kretzner, Leo; King, Michael; Street, Alasdair J.; Witte, Owen N.; Eisenman, Robert N.

In: Molecular Biology of the Cell, Vol. 5, No. 5, 05.1994, p. 597-609.

Research output: Contribution to journalArticle

Blackwood, EM, Lugo, TG, Kretzner, L, King, M, Street, AJ, Witte, ON & Eisenman, RN 1994, 'Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein', Molecular Biology of the Cell, vol. 5, no. 5, pp. 597-609.
Blackwood EM, Lugo TG, Kretzner L, King M, Street AJ, Witte ON et al. Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein. Molecular Biology of the Cell. 1994 May;5(5):597-609.
Blackwood, Elizabeth M. ; Lugo, Tracy Gross ; Kretzner, Leo ; King, Michael ; Street, Alasdair J. ; Witte, Owen N. ; Eisenman, Robert N. / Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein. In: Molecular Biology of the Cell. 1994 ; Vol. 5, No. 5. pp. 597-609.
@article{4ff4b0147f14450abc1ab1eecb449f0b,
title = "Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein",
abstract = "Activation of the c-myc proto-oncogene by chromosomal translocation or proviral insertion frequently results in the separation of the c-myc coding region from its normal regulatory elements. Such rearrangements are often accompanied by loss or mutation of c-myc exon 1 sequences. These genetic alterations do not affect synthesis of the major c-myc protein, p64, which is initiated from the first AUG codon in exon 2. However they can result in mutation or loss of the CUG codon located in exon 1 that normally serves as an alternative translational initiation codon for synthesis of an N- terminally extended form of c-Myc (p67). It has been hypothesized that p67 is a functionally distinct form of c-Myc whose specific loss during c-myc rearrangements confers a selective growth advantage. Here we describe experiments designed to test the functional properties of the two c-Myc protein forms. We introduced mutations within the translational initiation codons of a normal human c-myc cDNA that alter the pattern of Myc protein synthesis (p64 vs. p67). The functions of each of these proteins were experimentally addressed using co-transformation and transcriptional activation assays. Both the p64 and p67 c-Myc proteins were independently able to collaborate with bcr-abl in the transformation of Rat-1 fibroblasts. In addition, both the exon 1- and exon 2-initiated forms of the c-Myc protein stimulated transcription of a Myc/Max-responsive reporter construct to a similar level. Given the apparent absence of functional differences between p64 and p67, we conclude that the basis for c-Myc oncogenic activation lies primarily in the overall deregulation of its expression and not in alterations in the protein. The existence of the CUG translational initiator may reflect a mechanism for the continued synthesis of c-Myc protein under conditions where AUG initiation is inhibited.",
author = "Blackwood, {Elizabeth M.} and Lugo, {Tracy Gross} and Leo Kretzner and Michael King and Street, {Alasdair J.} and Witte, {Owen N.} and Eisenman, {Robert N.}",
year = "1994",
month = "5",
language = "English",
volume = "5",
pages = "597--609",
journal = "Molecular Biology of the Cell",
issn = "1059-1524",
publisher = "American Society for Cell Biology",
number = "5",

}

TY - JOUR

T1 - Functional analysis of the AUG- and CUG-initiated forms of the c-Myc protein

AU - Blackwood, Elizabeth M.

AU - Lugo, Tracy Gross

AU - Kretzner, Leo

AU - King, Michael

AU - Street, Alasdair J.

AU - Witte, Owen N.

AU - Eisenman, Robert N.

PY - 1994/5

Y1 - 1994/5

N2 - Activation of the c-myc proto-oncogene by chromosomal translocation or proviral insertion frequently results in the separation of the c-myc coding region from its normal regulatory elements. Such rearrangements are often accompanied by loss or mutation of c-myc exon 1 sequences. These genetic alterations do not affect synthesis of the major c-myc protein, p64, which is initiated from the first AUG codon in exon 2. However they can result in mutation or loss of the CUG codon located in exon 1 that normally serves as an alternative translational initiation codon for synthesis of an N- terminally extended form of c-Myc (p67). It has been hypothesized that p67 is a functionally distinct form of c-Myc whose specific loss during c-myc rearrangements confers a selective growth advantage. Here we describe experiments designed to test the functional properties of the two c-Myc protein forms. We introduced mutations within the translational initiation codons of a normal human c-myc cDNA that alter the pattern of Myc protein synthesis (p64 vs. p67). The functions of each of these proteins were experimentally addressed using co-transformation and transcriptional activation assays. Both the p64 and p67 c-Myc proteins were independently able to collaborate with bcr-abl in the transformation of Rat-1 fibroblasts. In addition, both the exon 1- and exon 2-initiated forms of the c-Myc protein stimulated transcription of a Myc/Max-responsive reporter construct to a similar level. Given the apparent absence of functional differences between p64 and p67, we conclude that the basis for c-Myc oncogenic activation lies primarily in the overall deregulation of its expression and not in alterations in the protein. The existence of the CUG translational initiator may reflect a mechanism for the continued synthesis of c-Myc protein under conditions where AUG initiation is inhibited.

AB - Activation of the c-myc proto-oncogene by chromosomal translocation or proviral insertion frequently results in the separation of the c-myc coding region from its normal regulatory elements. Such rearrangements are often accompanied by loss or mutation of c-myc exon 1 sequences. These genetic alterations do not affect synthesis of the major c-myc protein, p64, which is initiated from the first AUG codon in exon 2. However they can result in mutation or loss of the CUG codon located in exon 1 that normally serves as an alternative translational initiation codon for synthesis of an N- terminally extended form of c-Myc (p67). It has been hypothesized that p67 is a functionally distinct form of c-Myc whose specific loss during c-myc rearrangements confers a selective growth advantage. Here we describe experiments designed to test the functional properties of the two c-Myc protein forms. We introduced mutations within the translational initiation codons of a normal human c-myc cDNA that alter the pattern of Myc protein synthesis (p64 vs. p67). The functions of each of these proteins were experimentally addressed using co-transformation and transcriptional activation assays. Both the p64 and p67 c-Myc proteins were independently able to collaborate with bcr-abl in the transformation of Rat-1 fibroblasts. In addition, both the exon 1- and exon 2-initiated forms of the c-Myc protein stimulated transcription of a Myc/Max-responsive reporter construct to a similar level. Given the apparent absence of functional differences between p64 and p67, we conclude that the basis for c-Myc oncogenic activation lies primarily in the overall deregulation of its expression and not in alterations in the protein. The existence of the CUG translational initiator may reflect a mechanism for the continued synthesis of c-Myc protein under conditions where AUG initiation is inhibited.

UR - http://www.scopus.com/inward/record.url?scp=0028225186&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028225186&partnerID=8YFLogxK

M3 - Article

C2 - 7919540

AN - SCOPUS:0028225186

VL - 5

SP - 597

EP - 609

JO - Molecular Biology of the Cell

JF - Molecular Biology of the Cell

SN - 1059-1524

IS - 5

ER -