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Identification of three regions essential for interaction between a sigma-like factor and core RNA polymerase
P F Cliften1, J Y Park, B P Davis
1Department of Biochemistry and Molecular Genetics and Program in Molecular Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
Genes & Development
|November 14, 1997
Summary
Interactions between yeast mitochondrial RNA polymerase (Rpo41p) and its specificity factor (Mtf1p) involve multiple protein regions. Mutations in Mtf1p affecting core binding highlight conserved sigma factor domains crucial for holoenzyme formation.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Yeast mitochondrial RNA polymerase interactions serve as a model for complex enzymes.
- Understanding subunit interactions is key to deciphering transcriptional regulation.
Purpose of the Study:
- To analyze the interaction requirements between yeast core RNA polymerase (Rpo41p) and its sigma-like factor (Mtf1p).
- To identify specific regions and mutations in Mtf1p that affect core polymerase binding.
Main Methods:
- Two-hybrid assays and fusion protein constructs were employed.
- Analysis of point mutations in Mtf1p, including temperature-sensitive mutants.
- In vitro binding assays and structural modeling using E. coli sigma70.
Main Results:
- Full-length proteins are required for Rpo41p-Mtf1p interaction; truncations failed to interact.
- Nine of fifteen nonfunctional Mtf1p mutations lost interaction capability.
- Mutations cluster in conserved sigma factor regions (2 and 3), suggesting their importance in core binding.
Conclusions:
- Multiple regions across both Rpo41p and Mtf1p are essential for holoenzyme assembly.
- Conserved sigma factor domains are critical for mediating interactions with the core polymerase.
- Mutational analysis provides insights into the structural basis of RNA polymerase-specificity factor interactions.