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The essential sequence elements required for RNAP II carboxyl-terminal domain function in yeast and their
Pengda Liu1, Arno L Greenleaf, John W Stiller
1Department of Biology, East Carolina University, USA. pl1126@ecu.edu
Molecular Biology and Evolution
|January 23, 2008
Summary
The carboxyl-terminal domain (CTD) of RNA polymerase II has conserved sequence elements, Y(1)-Y(8) and S(2)-S(5)-S(9), essential for yeast function. These motifs and the phosphorylation cycle explain the CTD's conserved structure.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The carboxyl-terminal domain (CTD) of eukaryotic RNA polymerase II is crucial for transcription and nuclear events.
- Its conserved nature across eukaryotes, despite permissible variations, poses an evolutionary puzzle.
Purpose of the Study:
- To explain the strong conservation of the CTD in budding yeast.
- To identify specific sequence elements and functional constraints driving this conservation.
Main Methods:
- Comparative genomics and genetic complementation in yeast.
- In vitro kinase assays using GST-CTD fusion proteins.
Main Results:
- Identified two essential sequence elements within CTD heptapeptides: "Y(1)-Y(8)" and "S(2)-S(5)-S(9)".
- Demonstrated that increased distance between these functional units reduces phosphorylation efficiency by CTD-directed kinases.
- Showed that the RNAP II phosphorylation cycle likely drives purifying selection on the CTD structure.
Conclusions:
- The identified sequence motifs and phosphorylation cycle requirements provide a mechanistic explanation for the conserved CTD structure in yeast.
- These findings shed light on the evolutionary pressures maintaining the CTD's functional integrity.
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