Substrate specificity of the TRAMP nuclear surveillance complexes

Area of Science:

• Molecular Biology
• Yeast Genetics
• RNA Metabolism

Background:

• The RNA exosome and TRAMP complexes are essential for nuclear surveillance in yeast.
• TRAMP complexes consist of a DEAH-box RNA helicase (Mtr4), RNA-binding proteins (Air1/Air2), and a poly(A) polymerase (Trf4/Trf5).

Purpose of the Study:

• To investigate how TRAMP complexes target RNA substrates during nuclear surveillance.
• To elucidate the roles of individual TRAMP components in RNA binding specificity.

Main Methods:

• Mass spectrometry was used to identify TRAMP complexes and their associated proteins and RNAs in vivo.
• Analysis of TRAMP component binding sites and their colocalization with other nuclear RNA-binding proteins.
• Comparison of RNA abundance in wild-type and TRF5 deletion yeast strains.

Main Results:

• Three distinct TRAMP complexes were identified, each preferentially associating with different RNA classes.
• Trf4 and Trf5 were found to confer binding specificity for numerous RNA substrates, including pre-rRNAs and pre-mRNAs.
• TRAMP association with mRNAs revealed co-enrichment of functionally related transcripts, suggesting a role in gene expression regulation.
• TRF5 deletion led to reduced Mtr4 recruitment and increased RNA abundance for specific mRNAs bound by Trf5.

Conclusions:

• TRAMP complexes exhibit distinct substrate preferences, mediated significantly by Trf4 and Trf5 poly(A) polymerases.
• TRAMP-mediated RNA targeting plays a role in the regulation of gene expression through the surveillance pathway.
• Trf5 is crucial for Mtr4 recruitment and the proper turnover of specific mRNA targets.