P. Hidalgo et al., Recruitment of the transcriptional machinery through GAL11P: structure andinteractions of the GAL4 dimerization domain, GENE DEV, 15(8), 2001, pp. 1007-1020
The GAL4 dimerization domain (GAL4-dd) is a powerful transcriptional activa
tor when tethered to DNA in a cell bearing a mutant of the GAL11 protein, n
amed GAL11P. GAL11P (like GAL11) is a component of the RNA-polymerase II ho
loenzyme. Nuclear magnetic resonance (NMR) studies of GAL4-dd revealed an e
longated dimer structure with C-2 symmetry containing three helices that me
diate dimerization via coiled-coil contacts. The two loops between the thre
e coiled coils form mobile bulges causing a variation of twist angles betwe
en the helix pairs. Chemical shift perturbation analysis mapped the GAL11P-
binding site to the C-terminal helix alpha3 and the loop between alpha1 and
alpha2. One GAL11P monomer binds to one GAL4-dd dimer rendering the dimer
asymmetric and implying an extreme negative cooperativity mechanism. Alanin
e-scanning mutagenesis of GAL4-dd showed that the NMR-derived GAL11P-bindin
g face is crucial for the novel transcriptional activating function of the
GAL4-dd on GAL11P interaction. The binding of GAL4 to GAL11P, although an a
rtificial interaction, represents a unique structural motif for an activati
ng region capable of binding to a single target to effect gene expression.