GERM-CELL NUCLEAR FACTOR IS A RESPONSE ELEMENT-SPECIFIC REPRESSOR OF TRANSCRIPTION

We have shown that the orphan receptor Germ Cell Nuclear Factor (GCNF) binds to a direct repeat of the sequence AGGTCA with zero base pair s pacing (DR0). Here, we further characterize the binding characteristic s of GCNF. We demonstrate that GCNF binds specifically to DR0s as a ho modimer, and does not bind with high affinity to DR1-DR6 sequences, GC NF is the first nuclear receptor shown to bind specifically to DR0s. T he wild type GCNF is unable to transactivate the reporter plasmid DR0( 2)tkCAT. Lacking a ligand to activate GCNF, we fused the activation do main from the viral protein VP16 to GCNF, and observed activation of D R0(2)tkCAT. This activation is specifc to DR0s, and is not observed wh en that sequence is replaced by DR1-DR6 sequences. In addition GCNF do es not transactivate through an SF-1 response element. At increasing c oncentrations, wild type GCNF is able to repress basal transcription. Repression is again specific to DR0s. The preference of GCNF for the D R0 sequence both in vitro and in transfections suggests that GCNF defi nes a novel nuclear receptor signaling pathway. (C) 1998 Academic Pres s.