Coupled protein quality control during nonsense-mediated mRNA decay.

Translation of mRNAs containing premature termination codons (PTCs) results in truncated protein products with deleterious effects. Nonsense-mediated decay (NMD) is a surveillance pathway responsible for detecting PTC containing transcripts. Although the molecular mechanisms governing mRNA degradation have been extensively studied, the fate of the nascent protein product remains largely uncharacterized. Here, we use a fluorescent reporter system in mammalian cells to reveal a selective degradation pathway specifically targeting the protein product of an NMD mRNA. We show that this process is post-translational and dependent on the ubiquitin proteasome system. To systematically uncover factors involved in NMD-linked protein quality control, we conducted genome-wide flow cytometry-based screens. Our screens recovered known NMD factors but suggested that protein degradation did not depend on the canonical ribosome-quality control (RQC) pathway. A subsequent arrayed screen demonstrated that protein and mRNA branches of NMD rely on a shared recognition event. Our results establish the existence of a targeted pathway for nascent protein degradation from PTC containing mRNAs, and provide a reference for the field to identify and characterize required factors.

Metadata retrieval from sequence databases with ffq.

MOTIVATION: Several genomic databases host data and metadata for an ever-growing collection of sequence datasets. While these databases have a shared hierarchical structure, there are no tools specifically designed to leverage it for metadata extraction. RESULTS: We present a command-line tool, called ffq, for querying user-generated data and metadata from sequence databases. Given an accession or a paper's DOI, ffq efficiently fetches metadata and links to raw data in JSON format. ffq's modularity and simplicity make it extensible to any genomic database exposing its data for programmatic access. AVAILABILITY AND IMPLEMENTATION: ffq is free and open source, and the code can be found here: https://github.com/pachterlab/ffq.