Functional interaction between Ssu72 and the Rpb2 subunit of RNA polymerase II in Saccharomyces cerevisiae

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• SSU72 is an essential gene encoding a conserved protein with an unknown function.
• SSU72 interacts with the general transcription factor TFIIB.
• A mutation in SSU72 (ssu72-1) enhances TFIIB defects, causing heat sensitivity and altered transcription start site selection.

Purpose of the Study:

• To further define the function of the SSU72 protein.
• To investigate the interaction of SSU72 with the transcription machinery.
• To characterize a new SSU72 allele (ssu72-2) and its suppressors.

Main Methods:

• Isolation and characterization of suppressors for the ssu72-2 mutation.
• Sequence analysis of the rpb2-100 suppressor allele.
• Analysis of gene expression in mutant strains.
• Coimmunoprecipitation assays to assess protein interactions.

Main Results:

• A new allele, ssu72-2, causes a heat-sensitive phenotype.
• A suppressor mutation, rpb2-100, affects the second-largest subunit of RNA polymerase II (RNAP II).
• Both ssu72-2 and rpb2-100 mutations impair noninduced gene expression.
• SSU72 protein directly interacts with RNAP II.

Conclusions:

• SSU72 is a conserved factor involved in transcription initiation.
• SSU72 physically and functionally interacts with the RNAP II core machinery.
• Genetic interactions between ssu72 and rpb2 mutations stem from physical interactions.