TRANSCRIPTIONAL EFFECT OF ZFHEP IS REVERTED BY TPA TREATMENT
Knubel Carolina, Maldonado Noelia, Arroyo Daniela & Cabanillas, Ana María. CIBICI-CONICET, Fac CC QQ, Universidad Nacional de Córdoba. caroknubel@hotmail.com
The activity of a transcription factor (TF) can be controlled by posttranslational modification such as phosphorylation. Zfhep (Zinc Finger Homeodomain Enhancer-binding Protein) is a repressor of several genes and it is involved in lymphopoiesis, neurogenesis and myogenesis. Zfhep exists as two phosphorylated forms (P-Zfhep). EMSA done in our lab showed that the hypophosphorylated Zfhep binds to target genes stronger than the hyperphosphorylated Zfhep. Our goal was to test whether in vivo transcriptional effect of Zfhep is also altered by phosphorylation. Cell lines expressing one or both P-Zfhep were transfected with Zfhep expression vector and CD4, p73 y Zfhep/luciferase promoters by O/N Ca-P precipitation. Then, cells were incubated with 10 ng/ml phorbol esters (PMA) for 8 h. As expected luciferase activities (normalized by bgal) were diminished by Zfhep. TPA treatment reverted Zfhep repression of its target genes. The results show that phosphorylation is a possible mechanism of regulation of the transcriptional activity of this TF. Zfhep has been shown as a Smad interacting factor for eliciting TGF-b dependent gene activation in myogenesis. Zfhep would act as a cell-specific factor, and its phosphorylation status would provide a way to modulate the activity of TGF-b signaling pathway. Although PKC pathway seems to be involved in Zfhep phosphorylation, the present results do not rule out the involvement of TGF-b signal (also able to be regulated by PKC) in the process.
