A previously unidentified amino-terminal domain regulates transcriptional activity of wild-type and disease-associated human GLI2.
Zinc finger-containing Gli proteins mediate responsiveness to Hedgehog (Hh) signaling, with Gli2 acting as the major transcriptional activator in this pathway in mice. The discovery of disease-associated mutations points to a critical role for GLI2 in human Hh signaling as well. Here, we show that human GLI2 contains previously undescribed 5' sequence, extending the amino-terminus an additional 328 amino acids. In vitro, transcriptional activity of full-length GLI2 is up to 30 times lower than that of GLI2DeltaN (previously thought to represent the entire GLI2 protein), revealing the presence of an amino-terminal repressor domain in the full-length protein. GLI2DeltaN also exhibits potent transcriptional activity in vivo: overexpression in mouse skin leads to the formation of Hh-independent epithelial downgrowths resembling basal cell carcinomas, which in humans are associated with constitutive Hh signaling. The discovery of this additional, functionally relevant GLI2 sequence led us to re-examine several pathogenic human GLI2 mutants, now containing the entire amino-terminal domain. On the basis of the functional domains affected by the mutations, mutant GLI2 proteins exhibited either loss-of-function or dominant-negative activity. Moreover, deletion of the amino-terminus abrogated dominant-negative activity of mutant GLI2, revealing that this domain is required for transcriptional repressor activity of pathogenic GLI2. Our results establish the presence of an amino-terminal transcriptional repressor domain that plays a critical role in modulating the function of wild-type GLI2 and is essential for dominant-negative activity of a GLI2 mutant associated with human disease.
Medical Genetics Branch, NHGRI, NIH, Bethesda, MD 20892-3717, USA.
Erich
E
Roessler
Alexandre N
AN
Ermilov
Dorothy Katherine
DK
Grange
Aiqin
A
Wang
Marina
M
Grachtchouk
Andrzej A
AA
Dlugosz
Maximilian
M
Muenke
D000818:Animals; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000302:isolation & purification; D005260:Female; D006801:Humans; D007018:Hypopituitarism / Q000235:genetics; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010375:Pedigree; D017689:Polydactyly / Q000235:genetics; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D000075746:Zinc Finger Protein Gli2; D016335:Zinc Fingers
D018076:DNA, Complementary; C082593:GLI2 protein, human; D051741:Kruppel-Like Transcription Factors; D009687:Nuclear Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D000075746:Zinc Finger Protein Gli2