title: The Smads.
abstract: The Smads are a family of intracellular signalling molecules that act downstream of receptors for the transforming growth factor (TGF)-beta family of ligands. Three classes of Smads have been identified. The receptor-regulated Smads are direct substrates for the type I receptors, which are serine/threonine kinases. Once phosphorylated and activated, these Smads form hetero-oligomeric complexes with a second class of Smad, the common mediator Smads. These Smad complexes translocate to the nucleus, where they are recruited to DNA primarily by site-specific DNA binding transcription factors, and participate in regulating the transcription of target genes. Inhibitory Smads are the third identified class which antagonise the activity of the receptor-regulated Smads. Aberrant TGF-beta signalling has been associated with several human diseases such as cancer and fibrosis. The identification of the Smads as primary transducers of TGF-beta signals raises the possibility that agents directed at modulating Smad activity would have therapeutic applications.
authors.affiliation: Laboratory of Developmental Signalling, Imperial Cancer Research Fund, London, UK. c.hill@icrf.icnet.uk
authors.forename: C S
authors.initials: CS
authors.lastname: Hill
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000145:classification / Q000502:physiology*; D005355:Fibrosis / Q000209:etiology; D006801:Humans; D009369:Neoplasms / Q000209:etiology; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry* / Q000145:classification / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta