An Rpb4/Rpb7-like complex in yeast RNA polymerase III contains the orthologue of mammalian CGRP-RCP.
The essential C17 subunit of yeast RNA polymerase (Pol) III interacts with Brf1, a component of TFIIIB, suggesting a role for C17 in the initiation step of transcription. The protein sequence of C17 (encoded by RPC17) is conserved from yeasts to humans. However, mammalian homologues of C17 (named CGRP-RCP) are ... known to be involved in a signal transduction pathway related to G protein-coupled receptors, not in transcription. In the present work, we first establish that human CGRP-RCP is the genuine orthologue of C17. CGRP-RCP was found to functionally replace C17 in Deltarpc17 yeast cells; the purified mutant Pol III contained CGRP-RCP and had a decreased specific activity but initiated faithfully. Furthermore, CGRP-RCP was identified by mass spectrometry in a highly purified human Pol III preparation. These results suggest that CGRP-RCP has a dual function in mammals. Next, we demonstrate by genetic and biochemical approaches that C17 forms with C25 (encoded by RPC25) a heterodimer akin to Rpb4/Rpb7 in Pol II. C17 and C25 were found to interact genetically in suppression screens and physically in coimmunopurification and two-hybrid experiments. Sequence analysis and molecular modeling indicated that the C17/C25 heterodimer likely adopts a structure similar to that of the archaeal RpoE/RpoF counterpart of the Rpb4/Rpb7 complex. These RNA polymerase subunits appear to have evolved to meet the distinct requirements of the multiple forms of RNA polymerases.
Mesh Terms:
Amino Acid Sequence, Animals, Archaeal Proteins, Bacterial Proteins, Dimerization, Fungal Proteins, Humans, Macromolecular Substances, Mammals, Models, Molecular, Molecular Sequence Data, Mutation, Protein Conformation, RNA Polymerase II, RNA Polymerase III, Receptors, Calcitonin Gene-Related Peptide, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Sigma Factor, Suppression, Genetic, Transcription Factors, Yeasts
Amino Acid Sequence, Animals, Archaeal Proteins, Bacterial Proteins, Dimerization, Fungal Proteins, Humans, Macromolecular Substances, Mammals, Models, Molecular, Molecular Sequence Data, Mutation, Protein Conformation, RNA Polymerase II, RNA Polymerase III, Receptors, Calcitonin Gene-Related Peptide, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Sigma Factor, Suppression, Genetic, Transcription Factors, Yeasts
Mol. Cell. Biol.
Date: Jan. 01, 2003
PubMed ID: 12482973
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