RPC53 Encodes a Subunit of Saccharomyces cerevisiae RNA Polymerase C (III) Whose Inactivation Leads to a Predominantly G₁ Arrest

Abstract

RPC53 is shown to be an essential gene encoding the C53 subunit specifically associated with yeast RNA polymerase C (III). Temperature-sensitive rpc53 mutants were generated and showed a rapid inhibition of tRNA synthesis after transfer to the restrictive temperature. Unexpectedly, the rpc53 mutants preferentially arrested their cell division in the G_t phase as large, round, unbudded cells. The RPC53 DNA sequence is predicted to code for a hydrophilic M_r-46,916 protein enriched in charged amino acid residues. The carboxy-terminal 136 amino acids of C53 are significantly similar (25% identical amino acid residues) to the same region of the human BN51 protein. The BN51 cDNA was originally isolated by its ability to complement a temperature-sensitive hamster cell mutant that undergoes a cell division arrest, as is true for the rpc53 mutants.