The negative regulator of Gli, Suppressor of fused (Sufu), interacts with SAP18, Galectin3 and other nuclear proteins

Biochem J. 2004 Mar 1;378(Pt 2):353-62. doi: 10.1042/BJ20030786.

Abstract

Sufu (Suppressor of fused) is a negative regulator of the Hedgehog signal-transduction pathway, interacting directly with the Gli family of transcription factors. However, its function remains poorly understood. In the present study, we determined the expression, tissue distribution and biochemical properties of mSufu (mouse Sufu) protein. We identified several mSufu variants of which some were phosphorylated. A yeast two-hybrid screen with mSufu as bait allowed us to identify several nuclear proteins as potential partners of mSufu. Most of these partners, such as SAP18 (Sin3-associated polypeptide 18), pCIP (p300/CBP-cointegrator protein) and PIAS1 (protein inhibitor of activated signal transduction and activators of transcription 1), are involved in either repression or activation of transcription and two of them, Galectin3 and hnRNPA1 (heterogeneous nuclear ribonucleoprotein A1), have a nuclear function in pre-mRNA splicing. We confirmed the mSufu-SAP18 and mSufu-Galectin3 interactions by independent biochemical assays. Using a cell transfection assay, we also demonstrated that mSufu protein (484 amino acids) is predominantly cytoplasmic but becomes mostly nuclear when a putative nuclear export signal is mutated or after treatment of the cells with leptomycin B. Moreover, mSufu is translocated to the nucleus when co-expressed with SAP18, which is normally found in this compartment. In contrast, Galectin3 is translocated to the cytoplasm when it is co-expressed with mSufu. Our findings indicate that mSufu is a shuttle protein that appears to be extremely versatile in its ability to bind different proteins in both the cytoplasm and nucleus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagy-Related Proteins
  • Carrier Proteins / analysis
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism*
  • Embryo, Mammalian / metabolism
  • Galectin 3 / metabolism
  • Galectins
  • HeLa Cells
  • Histone Deacetylases
  • Humans
  • Macromolecular Substances
  • Mice
  • Nuclear Proteins / analysis
  • Nuclear Proteins / metabolism*
  • Oncogene Proteins / antagonists & inhibitors
  • Phosphorylation
  • Protein Sorting Signals
  • Repressor Proteins / analysis
  • Repressor Proteins / chemistry
  • Repressor Proteins / metabolism*
  • Saccharomyces cerevisiae Proteins
  • Tissue Distribution
  • Trans-Activators
  • Transcription Factors / analysis
  • Transcription Factors / antagonists & inhibitors
  • Transcription Factors / metabolism*
  • Zinc Finger Protein GLI1

Substances

  • ATG16 protein, S cerevisiae
  • Autophagy-Related Proteins
  • Carrier Proteins
  • Galectin 3
  • Galectins
  • Lgals3 protein, mouse
  • Macromolecular Substances
  • Nuclear Proteins
  • Oncogene Proteins
  • Protein Sorting Signals
  • Repressor Proteins
  • SAP18 protein, human
  • SUFU protein, human
  • Saccharomyces cerevisiae Proteins
  • Sap18 protein, mouse
  • Sufu protein, mouse
  • Trans-Activators
  • Transcription Factors
  • Zinc Finger Protein GLI1
  • Histone Deacetylases