All ‘long’ Grg
proteins can repress transactivation mediated by all Tcf family
members. Mouse B cell line IIAI.6 was co-transfected with the Tcf
reporter construct (containing either wild-type Tcf binding sites,
TOP-TK, or mutated Tcf binding sites, FOP-TK, as a negative control)
and a specific Tcf family member and β-catenin.
This results in transactivation and increase of luciferase activity.
Upon addition of increasing amounts of any of the Grg family members,
the luciferase activity decreases proportionally. (A)
Repression of Tcf-1-mediated transcriptional activation by Grg-1,
TLE-2, Grg-3 and Grg-4. (B) Repression of Lef-1-mediated
transcriptional activation by Grg-1, TLE-2, Grg-3 and Grg-4. (C) Repression of Tcf-3-mediated transcriptional
activation by Grg-1, TLE-2, Grg-3 and Grg-4. (D)
Repression of Tcf-4-mediated transcriptional activation by Grg-1,
TLE-2, Grg-3 and Grg-4. Transfections were performed in duplicate,
and results from one representative independent experiment are depicted
in each case. Luciferase values were corrected for the efficiency
of transfection using the internal Renilla transfection
control pRNL-TK by determining the luciferase/Renilla ratio.
This ratio is given on the y-axis, and was arbitrarily
set at 1 for the sample in which the TOP-TK reporter construct alone
was transfected.