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Molecular and Cellular Biology, June 2000, p. 4309-4319, Vol. 20, No. 12
Department of Molecular Biology, Princeton
University, Princeton, New Jersey 08544,1 and
Department of Cell Biology, Vanderbilt University School of
Medicine, Nashville, Tennessee 372322
Received 22 October 1999/Returned for modification 1 December
1999/Accepted 17 March 2000
We have assayed the oncogenic, proliferative, and apoptotic
activities of the frequent mutations that occur in the
c-myc gene in Burkitt's lymphomas. Some alleles have a
modest (50 to 60%) increase in transforming activity; however, the
most frequent Burkitt's lymphoma allele (T58I) had an unexpected
substantial decrease in transforming activity (85%). All alleles
restored the proliferation function of c-Myc in cells that grow slowly due to a c-myc knockout. There was discordance for some
alleles between apoptotic and oncogenic activities, but only
the T58A allele had elevated transforming activity with a concomitant
reduced apoptotic potential. We discovered a novel missense
mutation, MycS71F, that had a very low apoptotic activity
compared to wild-type Myc, yet this mutation has never been found in
lymphomas, suggesting that there is no strong selection for
antiapoptotic c-Myc alleles. MycS71F also induced very low
levels of cytochrome c release from mitochondria,
suggesting a mechanism of action for this mutation. Phosphopeptide
mapping provided a biochemical basis for the dramatically different
biological activities of the transformation-defective T58I and
transformation-enhanced T58A c-Myc alleles. Furthermore, the
antiapoptotic survival factor insulin-like growth factor 1 was found to suppress phosphorylation of T58, suggesting that the c-Myc
transactivation domain is a direct target of survival signals.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The c-Myc Transactivation Domain Is a Direct
Modulator of Apoptotic versus Proliferative Signals
*
Corresponding author. Mailing address: Department of
Molecular Biology, Princeton University, Princeton, NJ 08544. Phone: (609) 258-5936. Fax: 609-258-2759. E-mail:
mcole{at}molbio.princeton.edu.
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