Regulation of DNA binding by Rel/NF-kappa B transcription factors: structural views

Rel/NF-kappa B transcription factors form homo- and heterodimers with diffe rent DNA binding site specificities and DNA binding affinities. Several int racellular pathways evoked by a wide range of biological factors and enviro nmental conditions can lead to the activation of Rel/NF-kappa B dimers by s ignaling degradation of the inhibitory I kappa B protein. In the nucleus Re l/NF-kappa B dimers modulate the expression of a variety of genes including those encoding cytokines, growth factors, acute phase response proteins, i mmunoreceptors, other transcription factors, cell adhesion molecules, viral proteins and regulators of apoptosis, The primary focus of this review is on structural and functional aspects of Rel/NF kappa B:DNA complexes and th eir formation. The salient features of the Rel/NF-kappa B dimer:DNA structu re are described, as are modes of transcriptional regulation by phosphoryla tion, altered DNA binding properties, varying protein conformations, and in teractions with I kappa B proteins.