Abstract
The Pea3 transcription factor (which belongs to the PEA3 group) from the Ets family has been shown to be involved in mammary embryogenesis and oncogenesis. However, except for proteinases, only few of its target genes have been reported. In the present report, we identified bax as a Pea3 up-regulated gene. We provide evidence of this regulation by using Pea3 overexpression and Pea3 silencing in a mammary cell line. Both Pea3 and Erm, another member of the PEA3 group, are able to transactivate bax promoter fragments. Although the minimal Pea3-regulated bax promoter does not contain an Ets-binding site, two functional upstream stimulatory factor-regulated E boxes are present. We further demonstrate the ability of Pea3 and USF-1 to cooperate for the transactivation of the bax promoter, mutation of the E boxes dramatically reducing the Pea3 transactivation potential. Although Pea3 did not directly bind to the minimal bax promoter, we provide evidence that USF-1 could form a ternary complex with Pea3 and DNA. Taken together, our results suggest that Pea3 may regulate bax transcription via the interaction with USF-1 but without binding to DNA.
Highlights
Pea3, called E1AF or ETV4, is the founding member of a subfamily of ets genes that includes Er81 and Erm, which have been currently characterized in mice [1,2,3], humans (4 – 6), rats, dogs (Telgman, GenBankTM accession number AJ313194), chicken [7], zebrafish [8], and amphibian Xenopus [9]
Many reports argue for their involvement in the different stages of normal mammary gland development and in the events leading to mammary oncogenesis and metastasis [15, 54]
We report that Pea3 can regulate the expression of the bax gene in the TAC-2.1 normal mammary cell line, by using either Pea3-overexpressing cells or cells in which Pea3 expression was abolished by RNA interference
Summary
Called E1AF or ETV4, is the founding member of a subfamily of ets genes that includes Er81 (or ETV1) and Erm (or ETV5), which have been currently characterized in mice [1,2,3], humans (4 – 6), rats, dogs (Telgman, GenBankTM accession number AJ313194), chicken [7], zebrafish [8], and amphibian Xenopus [9] These three factors share three functional highly conserved domains: a DNA binding domain [10], an amino-terminal transactivation domain [11], and a carboxylterminal domain involved in DNA binding and transactivation regulation [12, 13]. We found that Pea regulates the minimal bax promoter, not by binding to a consensual Ets-binding site but via
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