RPC40, a unique gene for a subunit shared between yeast RNA polymerases A and C

Area of Science:

• Molecular Biology
• Yeast Genetics
• Gene Expression

Background:

• Yeast RNA polymerases A and C share a common subunit, approximately 40 kDa.
• The specific gene encoding this shared subunit was previously unidentified.

Purpose of the Study:

• To identify, sequence, and characterize the gene encoding the shared 40 kDa subunit of yeast RNA polymerases A and C.
• To investigate the function and essentiality of this subunit for cell viability and RNA polymerase synthesis.

Main Methods:

• Gene identification, sequencing, and in vitro mutagenesis of the AC40 subunit gene (RPC40).
• Development of a novel plasmid-shuffling method to isolate temperature-sensitive (ts) mutants.
• Analysis of RNA polymerase synthesis in ts mutants at restrictive temperatures.

Main Results:

• The RPC40 gene is unique, essential for yeast cell viability, and encodes a 37.6 kDa protein.
• The RPC40 promoter contains regulatory sequences found in RNA polymerase C and translational apparatus genes.
• A ts mutant (ts4) demonstrated impaired synthesis of RNA polymerases A and C, but not B, at the restrictive temperature.

Conclusions:

• The RPC40 gene product is a crucial component required for the synthesis of yeast RNA polymerases A and C.
• This subunit plays a specific role in the biogenesis of RNA polymerases A and C, distinct from RNA polymerase B.