Activation mutants in yeast RNA polymerase II subunit RPB3 provide evidence for a structurally conserved surface required for activation in eukaryotes and bacteria.
We have identified a mutant in RPB3, the third-largest subunit of yeast RNA polymerase II, that is defective in activator-dependent transcription, but not defective in activator-independent, basal transcription. The mutant contains two amino-acid substitutions, C92R and A159G, that are both required for pronounced defects in activator-dependent transcription. Synthetic enhancement of phenotypes of C92R and A159G, and of several other pairs of substitutions, is consistent with a functional relationship between residues 92-95 and 159-161. Homology modeling of RPB3 on the basis of the crystallographic structure of alphaNTD indicates that residues 92-95 and 159-162 are likely to be adjacent within the structure of RPB3. In addition, homology modeling indicates that the location of residues 159-162 within RPB3 corresponds to the location of an activation target within alphaNTD (the target of activating region 2 of catabolite activator protein, an activation target involved in a protein-protein interaction that facilitates isomerization of the RNA polymerase promoter closed complex to the RNA polymerase promoter open complex). The apparent finding of a conserved surface required for activation in eukaryotes and bacteria raises the possibility of conserved mechanisms of activation in eukaryotes and bacteria.
Tan
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University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Department of Molecular Genetics and Microbiology, Piscataway, New Jersey 08854, USA.
Linask
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KL
Ebright
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RH
Woychik
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NA
D000595:Amino Acid Sequence; D001419:Bacteria / Q000201:enzymology*; D015152:Blotting, Northern; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D005786:Gene Expression Regulation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D011401:Promoter Regions, Genetic; D017433:Protein Structure, Secondary; D012319:RNA Polymerase II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D029701:Saccharomyces cerevisiae Proteins; D012319:RNA Polymerase II; C112110:RPB3 protein, S cerevisiae