TFIIIA and homologous genes. The 'finger' proteins

Differential regulation of gene expression, in a precise temporal and spatial pattern during development, is thought to be partly mediated by site specific DNA binding proteins which promote a selective activation of gene transcription. From studies on Xenopus TFIIIA, a factor selectively required for transcription of 5 S ribosomal RNA genes, Miller et al. proposed a novel structural model of interaction between DNA and DNA binding protein. The striking homology of TFIIIA with several recently sequenced Drosophila and yeast gene products suggests that multiple regulatory proteins may have evolved from a small ancestral DNA binding protein domain and that the characteristic features of TFIIIA and TFIIIA-5S DNA interactions may be of general significance.