A model in vitro system for co-transcriptional splicing

Area of Science:

• Molecular Biology
• Gene Expression
• RNA Processing

Background:

• Metazoan RNA polymerase II transcripts feature small exons and large introns.
• Splicing, the removal of introns, is known to occur co-transcriptionally, before transcript release.

Purpose of the Study:

• To establish an efficient in vitro model system for studying co-transcriptional splicing.
• To investigate the mechanism of splicing while transcripts are still associated with RNA polymerase II.

Main Methods:

• Developed an in vitro system using immobilized CMV-DNA constructs to generate RNA polymerase II transcripts.
• Utilized RNase H to cleave nascent transcripts within the intron.
• Analyzed spliced products in fractions bound to RNA polymerase II.

Main Results:

• Demonstrated that elongating nascent transcripts remain tethered to RNA polymerase II.
• Showed efficient splicing of full-length nascent transcripts still attached to RNA polymerase II.
• Confirmed that both 5' and 3' intron cleavage fragments, still bound to RNA polymerase II, undergo splicing.

Conclusions:

• Established a robust in vitro system for co-transcriptional splicing.
• The spliceosome and its components are tethered to RNA polymerase II during splicing.
• Provides mechanistic insights into how splicing is coupled to transcription.