PARENT SESSION
SLIDE SESSION 11: GENE REGULATION & FUNCTION
Chairs: Michael Pallidino, Jeanne Wison-Rawles, Leslie Skalla (Trainee)
Univ Ottawa-Arts Hall 257
1:30 PM-3:30 PM

REPRESSION OF ETS-2 INDUCED TRANSACTIVATION OF THE INTERFERON-TAU PROMOTER BY OCT-4.

Ezashi, Toshihiko¹, Ghosh, Debjani¹, Roberts, Robert¹, ¹

ABSTRACT- Oct-4 is a POU-family transcription factor whose presence is associated with potential totipotency and an undifferentiated phenotype. Genes normally expressed in differentiated trophectoderm, but not in the cleavage stages of embryonic development, may be targets for silencing by Oct-4. Here, we have tested the hypothesis that the interferon- genes (IFN-), which are expressed exclusively in trophectoderm of bovine embryos, are transcriptionally silenced by Oct-4. Human JAr cells were transfected with truncated bovine IFN-1 promoters (-457, -353, -228, -126, -91 to +66), designed to eliminate potential octamer sites sequentially. Luciferase reporter expression from each of the promoters could be up-regulated up to 50-fold by Ets-2 as a result of an Ets-binding site located at -79 to -70, but this expression was approximately 90% silenced in the presence of Oct-4, even when the shortest promoter, which lacks any octamer-like site, was used. Full repression required both the amino (N) terminal and POU domains of Oct-4, but neither domain used alone was an effective silencer. Oct-4 and Ets-2 form a complex in vitro in the absence of DNA, through binding of the POU domain of Oct-4 to a docking site located between the pointed and DNA-binding domains of Ets-2. Oct-4, therefore, silences the IFN- promoter by quenching Ets-2 transactivation. The POU domain binds to Ets-2 directly, while the N-terminal inhibits transcription. These findings provide further evidence that the developmental switch to trophectoderm is accompanied by the loss of Oct-4 silencing of key genes. Supported by NIH grant HD 21896.

KEY WORDS: Ets-2, transcriptional silencing, interferon-tau, Oct-4