Nucleolar localization of the yeast RNA exosome subunit Rrp44 hints at early pre-rRNA processing as its main...

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The RNA exosome is a vital multisubunit protein complex responsible for RNA surveillance and processing across all RNA classes.
• It plays an essential role in pre-ribosomal RNA (pre-rRNA) processing and is conserved in archaea and eukaryotes.
• The exosome is known to localize to both the nucleus and cytoplasm in organisms like yeast and humans.

Purpose of the Study:

• To investigate the precise subcellular localization of the catalytically active subunit Rrp44/Dis3 of the RNA exosome in yeast (*Saccharomyces cerevisiae*).
• To determine the localization of other core exosome subunits, Rrp41 and Rrp43.
• To elucidate the functional implications of the exosome's localization in yeast.

Main Methods:

• Confocal microscopy was employed to analyze the subcellular localization of exosome subunits.
• Immunofluorescence techniques were used to visualize the Rrp44/Dis3, Rrp41, and Rrp43 proteins within yeast cells.

Main Results:

• The catalytically active subunit Rrp44/Dis3 was found to predominantly localize to the nucleus and concentrate within the nucleolus.
• Core exosome subunits Rrp41 and Rrp43 also showed significant nuclear localization, with strong accumulation in the nucleolus.
• These localization patterns suggest a primary role for the exosome in the nucleolus.

Conclusions:

• The yeast RNA exosome, including its active subunit Rrp44/Dis3 and core components Rrp41 and Rrp43, is mainly localized to the nucleus and highly concentrated in the nucleolus.
• This nucleolar enrichment strongly implicates the RNA exosome in the early stages of pre-rRNA processing and surveillance.
• The findings provide critical insights into the functional compartmentalization of this essential RNase complex.