A link between nuclear RNA surveillance, the human exosome and RNA polymerase II transcriptional termination

Area of Science:

• Molecular Biology
• RNA Processing
• Gene Expression

Background:

• Mature messenger RNA (mRNA) production in eukaryotes involves extensive transcript modification for nuclear export and cytoplasmic translation.
• mRNA processing defects can lead to transcript retention in the nucleus and degradation, often observed as nuclear foci.
• The precise mechanisms for recognizing and tethering defective RNAs remain largely unknown.

Purpose of the Study:

• To investigate the mechanism by which unprocessed transcripts are recognized and retained within the nucleus.
• To explore the role of the nuclear exosome and RNA polymerase II (Pol II) in this RNA quality control process.
• To elucidate the link between RNA surveillance, exosome function, and transcriptional termination.

Main Methods:

• Analysis of unprocessed β-globin transcripts in eukaryotic cells.
• Investigation of RNA polymerase II (Pol II) competency for termination.
• Assessment of the requirement for the nuclear exosome and Rrp6 in transcript tethering.

Main Results:

• Unprocessed β-globin transcripts were found to make RNA polymerase II (Pol II) incompetent for transcription termination.
• This quality control process was dependent on the integrity of the nuclear exosome.
• Unprocessed pre-mRNAs were observed to remain tethered to the DNA template, associated with Pol II, in an Rrp6-dependent manner.

Conclusions:

• Nuclear RNA surveillance actively retains defective transcripts by linking them to the transcription machinery.
• The nuclear exosome and Rrp6 play critical roles in tethering unprocessed pre-mRNAs to the DNA template.
• This study reveals a novel connection between nuclear RNA surveillance, the exosome, and the regulation of Pol II transcriptional termination.