Construction and Characterization of a Chimeric Transcription Factor: EWS-PEA3

Abstract

The activity of PEA3, a member of the Ets proto-oncogene family of transcription factors, is associated with various normal and aberrant developmental processes. PEA3 is believed to function in vivo as a transcription factor which regulates the gene expression of its cellular targets. In particular, PEA3 motifs are found in the regulatory regions of several genes implicated in tumor progression and metastasis. Aberrant PEA3 activity has been linked to the development and progression of several types of cancer, particularly, breast cancer and Ewing's sarcoma. To assist in the understanding of the role that PEA3 plays in these processes, constitutively-activated alleles of PEA3 were created by fusing a segment of the EWS gene to murine PEA3; to essentially mimic the EWS-Ets fusion proteins isolated from the human cancer syndrome, Ewing's sarcoma. Five EWS-PEA3 chimeric genes were constructed and one (EWSΔN268PEA3), is an exact murine version of an EWS-human PEA3 fusion gene isolated from Ewing's sarcoma. Transcriptional analysis of the EWS-PEA3 chimeras revealed that with the exception of one mutant, all the chimeras possessed increased transcriptional activity in comparison to normal PEA3 . Furthermore, it was suggested that the transcriptional activity of the chimeras may be regulated by Ras, although this observation requires additional validation. The chimeras were not found to possess any transforming activity, however, this finding does not suggest that the chimeras are not oncogenic in nature. In conclusion, these findings suggest that the EWS-PEA3 chimeras may indeed function as activated versions of the PEA3 transcription factor.