Nuclear surveillance and degradation of aberrant RNA requires the TRAMP complex, which promotes exosome-mediated degradation in the nucleus by adding poly (A) tails to aberrant RNAs. Interestingly, a mutant yeast strain defective in nuclear export of 60S preribosomes (sda1-2) accumulates ribosomal proteins, the TRAMP complex and the nuclear exosome in a punctate nucleolar structure, suggesting that preribosomes are degraded here.
To address if in this structure is a general site for TRAMP-exosome mediated degradation of polyadenylated non-coding RNAs, I will use several fluorescence microscopy detection techniques to determine if other known degradation enzymes and non-coding RNAs targeted for degradation accumulate in this focus. Pre-mRNA surveillance by the nuclear exosome involves interactions with chromatin, transcription elongation factors, pre-mRNA processing factors and export factors and likely occurs co-transcriptionally. To determine if a similar surveillance mechanism exists for pre-rRNA processing.
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