The RNA Exosome Adaptor ZFC3H1 Functionally Competes with Nuclear Export Activity to Retain Target Transcripts

Publication date: 15 May 2018
Source:Cell Reports, Volume 23, Issue 7
Author(s): Toomas Silla, Evdoxia Karadoulama, Dawid Mąkosa, Michal Lubas, Torben Heick Jensen
Mammalian genomes are promiscuously transcribed, yielding protein-coding and non-coding products. Many transcripts are short lived due to their nuclear degradation by the ribonucleolytic RNA exosome. Here, we show that abolished nuclear exosome function causes the formation of distinct nuclear foci, containing polyadenylated (pA⁺) RNA secluded from nucleocytoplasmic export. We asked whether exosome co-factors could serve such nuclear retention. Co-localization studies revealed the enrichment of pA⁺ RNA foci with "pA-tail exosome targeting (PAXT) connection" components MTR4, ZFC3H1, and PABPN1 but no overlap with known nuclear structures such as Cajal bodies, speckles, paraspeckles, or nucleoli. Interestingly, ZFC3H1 is required for foci formation, and in its absence, selected pA⁺ RNAs, including coding and non-coding transcripts, are exported to the cytoplasm in a process dependent on the mRNA export factor AlyREF. Our results establish ZFC3H1 as a central nuclear pA⁺ RNA retention factor, counteracting nuclear export activity.

Graphical abstract

Teaser

Silla et al. report that the RNA exosome adaptor protein ZFC3H1 acts as a nuclear RNA retention factor. In the absence of ZFC3H1, exosome targets are exported to the cytoplasm in a AlyREF-dependent manner. The discovery establishes ZFC3H1 as a central factor in the retention and degradation of polyadenylated RNA.


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