title: AF10-dependent transcription is enhanced by its interaction with FLRG.
abstract: BACKGROUND
  FLRG (follistatin-related gene) is a secreted glycoprotein which is very similar to follistatin. As observed for follistatin, FLRG is involved in the regulation of various biological processes through its binding to members of the TGFbeta (transforming growth factor beta) superfamily, activin, BMPs (bone morphogenetic proteins) and myostatin. Unlike follistatin, FLRG has been found to be both secreted and localized within the nucleus of many FLRG-producing cells, suggesting the existence of specific intracellular functions of the protein.
  
  
  RESULTS
  In order to analyse the function of the nuclear form of FLRG, we performed a yeast two-hybrid screen, in which we identified AF10 [ALL1 (acute lymphoblastic leukaemia) fused gene from chromosome 10], a translocation partner of the MLL (mixed-lineage leukaemia) oncogene in human leukaemia, as a FLRG-interacting protein. This interaction was confirmed by far-Western-blot analysis and co-immunoprecipitation with transfected COS-7 cells. The N-terminal region of AF10, including the PHD (plant homeodomain), is sufficient to mediate this interaction, and has been shown to be involved in AF10 homo-oligomerization. By immunoprecipitation experiments, we showed that FLRG enhances the homo-oligomerization of AF10. Functional studies demonstrated that FLRG enhances the transactivation properties of the AF10 protein fused to Gal4 DNA-binding domains in transient transfection assays.
  
  
  CONCLUSIONS
  Our present study provides novel insights into the function of the nuclear form of the FLRG protein, which is revealed as a novel regulator of transcription. The nuclear isoform of FLRG lacks an intrinsic transactivation domain, but enhances AF10-mediated transcription, probably through promoting the homo-oligomerization of AF10, thus facilitating the recruitment of co-activators.
authors.affiliation: Inserm, U590, Centre Léon Bérard, Université Lyon 1, Lyon, F-69003, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Forissier
authors.forename: Diane
authors.initials: D
authors.lastname: Razanajaona
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Ay
authors.forename: Sylvie
authors.initials: S
authors.lastname: Martel
authors.forename: Laurent
authors.initials: L
authors.lastname: Bartholin
authors.forename: Ruth
authors.initials: R
authors.lastname: Rimokh
mesh_terms: D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D038702:Follistatin-Related Proteins / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques
chemical_list: D038702:Follistatin-Related Proteins; C092513:MLLT10 protein, human; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors