The recent identification of the Smad proteins has allowed the delineation of a mechanism by which TGF-β and related growth and differentiation factors convey their signals from transmembrane receptors into nucleus. Following receptor-induced activation heteromeric Smad complexes translocate into the nucleus where they act as transcription factors. Smad proteins modulate target genes through interaction with DNA and with other nuclear factors. Disruption of signalling cascade by Smad gene aberrations may cause loss of cellular responsiveness to TGF-β and thus contribute to development of cancer.
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