Elevated expression of Ets2 or distinct portions of Ets2 can reverse Ras-mediated cellular transformation.
Ets transcription factors are important downstream targets of oncogenic Ras. The transcriptional activity of several Ets family members is regulated by Ras, and interfering with Ets-dependent transcription by expression of just the Ets2 DNA binding domain can inhibit or reverse Ras-mediated cellular transformation. To better understand the role of Ets proteins in Ras transformation, we have now analyzed the effects of stably expressing a variety of Ets2 constructs in Ras-transformed NIH3T3 (DT) cells. Expression of only the Ets2 transactivation domains, which also inhibits Ras or Neu/ErbB-2-mediated activation of Ets-dependent transcription, strongly inhibited anchorage-independent growth, but did not revert the transformed DT cell morphology. Unexpectedly, high expression of full-length Ets2, a transcriptional activator, broadly reversed the transformed properties of DT cells, including anchorage-independent growth, transformed morphology, and tumorigenicity, but did not impair attached cell growth. Increasing full-length Ets2 transcriptional activity by fusing it to the VP16 transactivation domain enhanced its ability to reverse DT cell transformation. Mutational analysis revealed that the mitogen-activated protein kinase phosphorylation site required for Ras-mediated activation, Ets2(T72), was not essential for Ets2 reversion activity. The distinct reversion activities of the highly expressed Ets2 transactivation domains or full-length Ets2, along with the specific reversion activity by Ets2 constructs that either inhibit or activate Ets-dependent transcription, suggests multiple roles for Ets factors in cellular transformation. These results indicate that several distinct approaches for modulating Ets activity may be useful for intervention in human cancers.
Foos
G
G
La Jolla Cancer Research Center, The Burnham Institute, La Jolla, California 92037, USA.
García-Ramírez
J J
JJ
Galang
C K
CK
Hauser
C A
CA
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D002471:Cell Transformation, Neoplastic; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D011905:Genes, ras; D006801:Humans; D051379:Mice; D010641:Phenotype; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D012097:Repressor Proteins / Q000096:biosynthesis*; D015534:Trans-Activators; D014157:Transcription Factors
D004268:DNA-Binding Proteins; C107465:ERF protein, human; C494069:ETS2 protein, human; C494070:Ets2 protein, mouse; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA