Analysis of Schizosaccharomyces pombe mediator reveals a set of essential subunits conserved between yeast and metazoan cells.

Department of Medical Nutrition, Karolinska Institute, Novum, S-141 86 Huddinge, Sweden.
With the identification of eight new polypeptides, we here complete the subunit characterization of the Schizosaccharomyces pombe RNA polymerase II holoenzyme. The complex contains homologs to all 10 essential gene products present in the Saccharomyces cerevisiae Mediator, but lacks clear homologs to any of the 10 S. cerevisiae components encoded by nonessential genes. S. pombe Mediator instead contains three unique components (Pmc2, -3, and -6), which lack homologs in other cell types. Presently, pmc2(+) and pmc3(+) have been shown to be nonessential genes. The data suggest that S. pombe and S. cerevisiae share an essential protein module, which associates with nonessential speciesspecific subunits. In support of this view, sequence analysis of the conserved yeast Mediator components Med4 and Med8 reveals sequence homology to the metazoan Mediator components Trap36 and Arc32. Therefore, 8 of 10 essential genes conserved between S. pombe and S. cerevisiae also have a metazoan homolog, indicating that an evolutionary conserved Mediator core is present in all eukaryotic cells. Our data suggest a closer functional relationship between yeast and metazoan Mediator than previously anticipated.
Mesh Terms:
Amino Acid Sequence, Animals, Conserved Sequence, Fungal Proteins, Holoenzymes, Humans, Mediator Complex, Molecular Sequence Data, Nuclear Proteins, RNA Polymerase II, Saccharomyces cerevisiae Proteins, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Sequence Homology, Amino Acid, Trans-Activators, Transcription Factors, Transcriptional Activation, Yeasts
Proc. Natl. Acad. Sci. U.S.A. Oct. 09, 2001; 98(21);11985-90 [PUBMED:11572939]
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