Downstream sequence-dependent RNA cleavage and pausing by RNA polymerase I.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA sequence is known to influence transcription rates by DNA-dependent RNA polymerases.
• The specific impact of DNA sequence on the transcription elongation properties of eukaryotic RNA polymerase I (Pol I) remains largely undefined.

Purpose of the Study:

• To investigate how downstream DNA sequences influence the transcription elongation of RNA polymerase I (Pol I) in Saccharomyces cerevisiae.
• To elucidate the effects of DNA sequence on Pol I pausing, elongation complex stability, and nucleolytic cleavage activity.

Main Methods:

• In vitro transcription assays to assess Pol I pausing and cleavage in response to varying downstream DNA sequences.
• Analysis of native elongating transcript sequencing (NET-seq) data from Saccharomyces cerevisiae to correlate Pol I occupancy with downstream DNA sequence composition.

Main Results:

• AT-rich downstream DNA significantly enhances Pol I pausing and inhibits its nucleolytic cleavage activity in vitro.
• In vivo, Pol I occupancy increases with increasing downstream AT content and decreases with increasing downstream GC content.
• These findings demonstrate that downstream DNA sequences directly impact the kinetics of Pol I transcription elongation.

Conclusions:

• The DNA sequence immediately downstream of the transcription start site plays a critical role in regulating Pol I elongation kinetics.
• Both in vitro and in vivo evidence indicates that Pol I transcription is sensitive to the local DNA sequence environment.
• Understanding these sequence-dependent effects is crucial for comprehending gene regulation by RNA polymerase I.