The conserved and non-conserved regions of Rpb4 are involved in multiple phenotypes in Saccharomyces cerevisiae.
Rpb4, the fourth largest subunit of RNA polymerase II in Saccharomyces cerevisiae, is required for many phenotypes, including growth at high and low temperatures, sporulation, pseudohyphal growth, activated transcription of a subset of genes, and efficient carbon and energy metabolism. We have used deletion analysis to delineate the domains of the protein involved in these multiple phenotypes. The scRpb4 protein is conserved at the N and C termini but possesses certain non-conserved regions in the central portion. Our deletion analysis and molecular modeling results show that the N- and C-terminal conserved regions of Rpb4 are involved in interaction with Rpb7, the Rpb4 interacting partner in the RNA polymerase II. We further show that the conserved N terminus is required for efficient activated transcription from the INO1 promoter but not the GAL10- or the HSE-containing promoters. The N terminus is not required for any of the stress responses tested: growth at high temperatures, sporulation, and pseudohyphal growth. The conserved C-terminal 23 amino acids are not required for the role of Rpb4 in the pseudohyphal growth phenotype but might play a role in other stress responses and activated transcription. From the deletion analysis of the non-conserved regions, we report that they influence phenotypes involving both the N and C termini (interaction with Rpb7 and transcription from the INO1 promoter) but not any of the stress-responsive phenotypes tested suggesting that they might be involved in maintaining the two conserved domains in an appropriate conformation for interaction with Rpb7 and other proteins. Taken together, our results allow us to assign phenotype-specific roles for the different conserved and non-conserved regions of Rpb4.
Sampath
Vinaya
V
Department of Microbiology & Cell Biology, Indian Institute of Science, Bangalore 560012, India.
Rekha
Nambudiry
N
Srinivasan
N
N
Sadhale
Parag
P
D000595:Amino Acid Sequence; D017124:Conserved Sequence; D006706:Homeostasis; D008958:Models, Molecular; D010641:Phenotype; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D017384:Sequence Deletion; D015533:Transcriptional Activation; D014161:Transduction, Genetic
D029701:Saccharomyces cerevisiae Proteins; D012319:RNA Polymerase II; C423309:RPB4 protein, S cerevisiae; C470553:RPB7 protein, S cerevisiae