Identifying a core RNA polymerase surface critical for interactions with a sigma-like specificity factor

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Transcription initiation involves cyclic interactions between RNA polymerase (RNAP) and initiation factors.
• Understanding subunit interactions within these complexes is crucial but remains limited.
• Yeast mitochondrial RNAP (Rpo41p) interacts with its sigma-like specificity factor (Mtf1p).

Purpose of the Study:

• To identify regions of yeast mitochondrial RNAP (Rpo41p) critical for interaction with its specificity factor (Mtf1p).
• To investigate the functional significance of these interacting regions in transcription initiation.

Main Methods:

• Utilized a two-hybrid selection approach starting with an interaction-defective Mtf1p mutant (V135A).
• Isolated suppressing mutations in the core RNAP (Rpo41p).
• Employed additional point mutations and biochemical assays for validation.

Main Results:

• Identified three distinct regions in Rpo41p that suppress Mtf1p interaction defects.
• These suppressor regions, when modeled, appear to form a single surface on the RNAP.
• Two suppressor regions are analogous to DNA recognition/melting sites in T7 RNAP, suggesting an alternative functional role in mitochondrial RNAP.

Conclusions:

• Specific regions on yeast mitochondrial RNAP (Rpo41p) are essential for interaction with Mtf1p.
• Mitochondrial RNAPs utilize a conserved surface for specificity factor interaction, distinct from phage RNAP DNA binding sites.
• This interaction is vital for promoter recognition and DNA melting, analogous to bacterial systems.