Carboxy-terminally truncated Gli3 proteins associate with Smads (original) (raw)

Zinc-finger transcription factors of the Gli family have important roles in animal development. Gli1 and Gli2 can act as mediators of hedgehog signals, whereas Gli3, and in some contexts Gli2, can act as an antagonist1,2,3,4,5. The finding that Gli3 and Gli2 are expressed adjacent to many sites of bone morphogenetic protein (BMP) expression, including the early ventral/posterior mesoderm, the limb bud and the dorsal neural tube1,2, raised the possibility that these Gli proteins interact with BMP signalling. Indeed, genetic analyses6 have hinted at an interaction between Gli3 and Bmp4. Human syndromes proposed to arise from mutations that produce carboxy-terminally truncated GLI3 proteins, such as Pallister-Hall syndrome7 (PHS) and polydactyly type A (PAP-A; ref. 8), have phenotypes that include mutant limbs reminiscent of those resulting from alterations in BMP function. It seems possible, therefore, that the function of C-terminally truncated Gli3 may affect BMP signalling, or vice versa, and that this could occur through interactions with Smad proteins; the latter being the intracellular transducers of TGFβ family signals, including BMPs (ref. 9).

To identify Gli3 regions involved in Smad interactions, we tested the Smad-binding activity of Gli3ĆΔClaI, two terminal deletions of Gli3ĆΔClaI that retained the zinc-finger region and Gli3ĆΔXhoI, which lacks the three C-terminal zinc fingers (Fig. 1_a_) shown to bind DNA directly in Gli1 (ref. 12). Gli3ĆΔClaI and the two deletion mutants maintaining an intact zinc-finger domain formed complexes with Smad1, and in all cases BMP signalling partially inhibited complex formation (Fig. 1_d_). Complex formation, however, was not detected with Gli3ĆΔXhoI (Fig. 1_d_), indicating that the last three zinc fingers are required for Smad binding. As the last three zinc fingers of Gli3 and Gli1 are approximately 98% identical and Gli3, but not Gli1, binds Smads, the Smad-binding activity of Gli3 is specific and is not due to the presence of generic zinc fingers. Moreover, in our assay, both Gli3ĆΔClaI, which approximates the PAP-A form, and Gli3ĆΔBal#8, which approximates the PHS form, bind Smads.

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Acknowledgements

This work was supported by NIH grants (NS37352) to A.R.A. and (CA34610) to J.M., a Basil O'Connor Award from the March of Dimes and a Pew fellowship to A.R.A. and a Cancer Center grant to MSKCC. J.M. is an investigator of the Howard Hughes Medical Institute.

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  1. Fang Liu
    Present address: Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, NJ, 08854, USA

Authors and Affiliations

  1. Memorial Sloan-Kettering Cancer Center, Cell Biology Program and Howard Hughes Medical Institute, New York, 10021, New York, USA
    Fang Liu & Joan Massagué
  2. Developmental Genetics Program and Department of Cell Biology, The Skirball Institute, NYU School of Medicine, 540 First Avenue, New York, 10016, New York, USA
    Ariel Ruiz i Altaba.

Authors

  1. Fang Liu
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  2. Joan Massagué
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  3. Ariel Ruiz i Altaba.
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Correspondence toJoan Massagué or Ariel Ruiz i Altaba..

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Liu, F., Massagué, J. & Altaba., A. Carboxy-terminally truncated Gli3 proteins associate with Smads.Nat Genet 20, 325–326 (1998). https://doi.org/10.1038/3793

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