Structural basis for the species-specific activity of TFIIS.
Many proteins involved in eukaryotic transcription are similar in function and in sequence between organisms. Despite the sequence similarities, there are many factors that do not function across species. For example, transcript elongation factor TFIIS is highly conserved among eukaryotes, and yet the TFIIS protein from Saccharomyces cerevisiae cannot function with mammalian RNA polymerase II and vice versa. To determine the reason for this species specificity, chimeras were constructed linking three structurally independent regions of the TFIIS proteins from yeast and human cells. Two independently folding domains, II and III, have been examined previously using NMR (). Yeast domain II alone is able to bind yeast RNA polymerase II with the same affinity as the full-length TFIIS protein, and this domain was expected to confer the species selectivity. Domain III has previously been shown to be readily exchanged between mammalian and yeast factors. However, the results presented here indicate that domain II is insufficient to confer species selectivity, and a primary determinant lies in a 30-amino acid highly conserved linker region connecting domain II with domain III. These 30 amino acids may physically orient domains II and III to support functional interactions between TFIIS and RNA polymerase II.
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA.
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Shimasaki
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Kane
D000595:Amino Acid Sequence; D017124:Conserved Sequence; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012319:RNA Polymerase II / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae; D013045:Species Specificity; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D035165:Transcription Factors, General; D035602:Transcriptional Elongation Factors
D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D035165:Transcription Factors, General; D035602:Transcriptional Elongation Factors; C018648:transcription factor S-II; D012319:RNA Polymerase II