V. Pouillon et al., TTF-2 DOES NOT APPEAR TO BE A KEY MEDIATOR OF THE EFFECT OF CYCLIC-AMP ON THYROGLOBULIN GENE-TRANSCRIPTION IN PRIMARY CULTURED DOG THYROCYTES, Biochemical and biophysical research communications, 242(2), 1998, pp. 327-331
TTF-2 is a thyroid-specific winged-helix transcription factor which ha
s been proposed to play a key role in the hormonal control of thyroglo
bulin and thyroperoxidase genes transcription in FRTL-5 cells. We have
analyzed TTF-2 DNA-binding activity in primary cultures of dog thyroc
ytes maintained in control condition or in the presence of the cAMP ag
onist forskolin. Binding of S-35-labelled nuclear proteins to the TTF-
2 recognition sequence identified the presence of two molecular specie
s of 41.5 and 42.5 kDa. TTF-2 DNA-binding activity was clearly detecta
ble in nuclear extracts from unstimulated cells and appeared increased
in forskolin-treated cells. Thus, the presence of TTF-2 DNA-binding a
ctivity does not correlate with the cAMP-dependent activity of thyrogl
obulin and thyroperoxidase genes in this cell system. In addition, the
mutation of the TTF-2 binding site in the thyroglobulin promoter resu
lted in a very reduced but still clearly cAMP-dependent promoter activ
ity when assayed by transient expression in the same cells. These resu
lts do not support a dominant role for TTF-2 in the cAMP-dependent con
trol of thyroglobulin gene transcription in primary cultured thyrocyte
s. (C) 1998 Academic Press.