Biology subjects

Lykke-Anderson, J.

Publications and source records attributed to Lykke-Anderson, J..

4 recordsLinked to original sources

bioRxiv2025

Multiple Quality Control Checkpoints Safeguard Small Nuclear RNA Biogenesis and Prevent Assembly of Aberrant Spliceosomes

Defective small nuclear (sn)RNAs are produced from hundreds of human snRNA pseudogenes and mutant snRNA genes associated with human developmental disorders. Machineries that prevent defective snRNAs from disrupting pre-mRNA splicing remain poorly defined. Here, we identify multiple checkpoints in snRNA biogenesis monitored by quality control machineries that subject defective snRNAs to degradation and prevent their assembly into spliceosomes. We show that variant U1 snRNAs produced from human pseudogenes, some at rates approaching the canonical snRNAs, are impaired in 3 cleavage and targeted for degradation by the NEXT-exosome while failures in subsequent protein assembly steps promote NEXT-exosome- or Terminal Uridylyl Transferase 4/7-mediated degradation. These pathways also repress mutant snRNAs associated with human developmental disorders. Impeding snRNA quality control causes formation of aberrant spliceosomes and altered pre-mRNA splicing. These findings define checkpoints in snRNA biogenesis that safeguard pre-mRNA splicing and represent potential therapeutic targets for human disorders associated with snRNA mutations.

molecular biology↗

bioRxiv2025

Post-transcriptional monoadenylation by TENT2 terminates human RNA polymerase III transcript 3' end processing and promotes 7SL RNA biogenesis

Small non-coding RNAs (sncRNAs) are subject to 3 end trimming and tailing activities that impact maturation versus degradation decisions during biogenesis. To investigate the dynamics of human sncRNA 3 end processing at a global level we performed genome-wide 3 end sequencing of nascently-transcribed and steady-state sncRNAs. This revealed widespread post-transcriptional adenylation of nascent sncRNAs, which came in two distinct varieties. One is characterized by oligoadenylation, which is transient, promoted by TENT4A/4B polymerases, and most commonly observed on unstable snoRNAs that are not fully processed at their 3 ends. The other is characterized by monoadenylation, which is broadly catalyzed by TENT2 and, in contrast to oligoadenylation, stably accumulates at the 3-end of sncRNAs, including Polymerase-III-transcribed (Pol-III) RNAs and a subset of small nuclear RNAs. Monoadenylation inhibits Pol-III RNA post-transcriptional 3 uridine trimming and extension and, in the case of 7SL RNAs, prevents their accumulation with nuclear La protein and promotes their biogenesis towards assembly into cytoplasmic signal recognition particles. Thus, the biogenesis of human sncRNAs involves widespread mono- or oligo-adenylation with divergent impacts on sncRNA fates.

molecular biology↗

bioRxiv2023

The 3' exonuclease TOE1 selectively processes snRNAs through recognition of Sm complex assembly and 5' cap trimethylation

Competing exonucleases that promote 3 end maturation or degradation direct quality control of small non-coding RNAs, but how these enzymes distinguish normal from aberrant RNAs is poorly understood. The Pontocerebellar Hypoplasia 7 (PCH7)-associated 3 exonuclease TOE1 promotes maturation of canonical small nuclear RNAs (snRNAs). Here, we demonstrate that TOE1 achieves specificity towards canonical snRNAs by recognizing Sm complex assembly and cap trimethylation, two features that distinguish snRNAs undergoing correct biogenesis from other small non-coding RNAs. Indeed, disruption of Sm complex assembly via snRNA mutations or protein depletions obstructs snRNA processing by TOE1, and in vitro snRNA processing by TOE1 is stimulated by a trimethylated cap. An unstable snRNA variant that normally fails to undergo maturation becomes fully processed by TOE1 when its degenerate Sm binding motif is converted into a canonical one. Our findings uncover the molecular basis for how TOE1 distinguishes snRNAs from other small non-coding RNAs and explain how TOE1 promotes maturation specifically of canonical snRNAs undergoing proper processing.

molecular biology↗

bioRxiv2022

The 2',3' cyclic phosphatase Angel1 facilitates mRNA degradation during human ribosome-associated quality control

Translation elongation stalls trigger mRNA decay and degradation of the nascent polypeptide via translation-dependent quality control pathways. One such pathway, non-stop mRNA decay (NSD), targets aberrant mRNAs that lack stop codons for example due to premature polyadenylation. Here we identify Angel1, a CCR4 deadenylase homolog whose biochemical activity remains poorly defined, as a rate-limiting factor for NSD in human cells. Angel1 associates with mRNA coding regions and proteins involved in ribosome-associated quality control and mRNA decay, consistent with a factor that monitors translation elongation stalls. Depletion of Angel1 causes stabilization of reporter mRNAs that are targeted for NSD by the absence of stop codons, but not an mRNA targeted for nonsense-mediated decay. A conserved catalytic residue of Angel1 is critical for its function in NSD. Our findings identify Angel1 as a human NSD factor and suggest that Angel1 catalytic activity plays a critical role in the NSD pathway.

molecular biology↗