The c-Myc transactivation domain is a direct modulator of apoptotic versus proliferative signals.

Chang DW, Claassen GF, Hann SR, Cole MD
Mol Cell Biol. 2000 20 (12): 4309-19

PMID: 10825194 · PMCID: PMC85798 · DOI:10.1128/MCB.20.12.4309-4319.2000

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.

MeSH Terms (10)

Animals Apoptosis Burkitt Lymphoma Cell Division Cell Line Gene Expression Regulation Genes, myc Humans Mutation, Missense Transfection

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