RNA polymerase II initiation factor interactions and transcription start site selection

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Transcription start site (TSS) location varies between yeast species like Schizosaccharomyces pombe and Saccharomyces cerevisiae.
• Differences in TSS positioning relative to the TATA box suggest distinct regulatory factors are involved.

Purpose of the Study:

• To identify the specific protein factors responsible for the differential positioning of transcription start sites in S. pombe and S. cerevisiae.
• To elucidate the functional interactions between general transcription factors and RNA polymerase II in determining TSS accuracy.

Main Methods:

• Reconstitution of an RNA polymerase II transcription system from S. pombe extracts.
• Component exchange experiments between S. pombe and S. cerevisiae transcription systems.
• Analysis of transcription start site location following component swapping.

Main Results:

• Individual exchange of transcription factor IIF (TFIIF) and transcription factor IIH (TFIIH) counterparts did not alter TSS location.
• TFIIB, TFIIE, and RNA polymerase II could not be individually exchanged, but pairwise exchanges (TFIIE-TFIIH, TFIIB-RNA polymerase II) were successful.
• The exchange of TFIIB and RNA polymerase II specifically shifted the transcription start site, indicating their critical role.

Conclusions:

• TFIIB and RNA polymerase II are the sole determinants of transcription start site positioning in these yeast systems.
• Functional interactions between TFIIB and RNA polymerase II are essential for accurate TSS selection.
• Understanding these factors provides insight into the fundamental mechanisms of eukaryotic transcription initiation.