Dataset Information

A COFRADIC protocol to study protein ubiquitination

ABSTRACT: We here apply the COmbined FRActional DIagonal Chromatography (COFRADIC) technology to enrich for ubiquitinated peptides and identify sites of ubiquitination by mass spectrometry. Our technology bypasses the need to ectopically overexpress tagged variants of ubiquitin and the use of sequence-biased antibodies recognizing ubiquitin remnants. In brief, all protein primary amino groups are blocked by chemical acetylation after which ubiquitin chains are proteolytically and specifically removed by the catalytic core domain of the USP2 deubiquitinase (USP2cc). As USP2cc cleaves the isopeptidyl bond between the ubiquitin C-terminus and the ?-amino group of the ubiquitinated lysine, this enzyme re-introduces primary ?-amino groups in proteins. These amino groups are then chemically modified with a handle that allows specific isolation of ubiquitinated peptides during subsequent COFRADIC chromatographic runs. Our method allowed us to identify over 8,200 endogenous ubiquitination sites in more than 3,600 different proteins in a native human Jurkat cell lysate.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Kris Gevaert

PROVIDER: MSV000080780 | MassIVE | Wed Mar 29 13:49:00 BST 2017

SECONDARY ACCESSION(S): PXD000934

REPOSITORIES: MassIVE

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A COFRADIC protocol to study protein ubiquitination.

Stes Elisabeth E Laga Mathias M Walton Alan A Samyn Noortje N Timmerman Evy E De Smet Ive I Goormachtig Sofie S Gevaert Kris K

Journal of proteome research 20140520 6

Here, we apply the COmbined FRActional DIagonal Chromatography (COFRADIC) technology to enrich for ubiquitinated peptides and to identify sites of ubiquitination by mass spectrometry. Our technology bypasses the need to overexpress tagged variants of ubiquitin and the use of sequence-biased antibodies recognizing ubiquitin remnants. In brief, all protein primary amino groups are blocked by chemical acetylation, after which ubiquitin chains are proteolytically and specifically removed by the cata ...[more]

PMID: 24816145

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Project description:Translation elongation rates are regulated to ensure proper conformation and biological function of proteins. Translation of either non-stop mRNA or transcripts coding for poly-basic sequences induces ribosome stalling, and the arrest product is degraded by the ribosome-mediated quality control system (RQC). During this process, the stalled ribosome is dissociated into subunits, and the polypeptide is ubiquitinated by the E3 ubiquitin ligase Listerin on the 60S large ribosomal subunit (LSU) leading to subsequent proteasomal degradation. However, it is largely unknown how stalled ribosomes are recognized and dissociated into subunits. Here we report that ubiquitination of the ribosomal protein uS10 by the E3 ubiquitin ligase Hel2 is required for the production of the RQC substrate. RQC-trigger (RQT) factors, a RNA helicase-family protein Slh1/Rqt2, ubiquitin binding protein Cue3/Rqt3 and yKR023W/Rqt4, were also required for the primary steps of RQC, and associated with Hel2-ribosome complexes. Rqt2-4 factors were dispensable for the ubiquitination of uS10 by Hel2/Rqt1 and associated with ribosomes independent of the ubiquitination of uS10. However, the ubiquitin-binding activity of Rqt3 were crucial to trigger RQC. Cryo-electron microscopy (cryo-EM) analysis revealed that Hel2 bound ribosomes are in an rotated state containing hybrid state AP- and PE-tRNAs. Furthermore, ribosome profiling revealed that short footprints, hallmarks of hybrid state ribosomes18, were accumulated at tandem CGA rare codons at the beginning of the poly arginine stalling sequence and long footprints at subsequent codons, respectively. Short footprints at CGA codons were decreased in rqt1 mutant but drastically increased in uS10 mutants defective in the ubiquitination or rqt2 mutant. Collectively, our results demonstrate that Hel2 stabilizes ratcheted ribosomes leading to ubiquitination of uS10. Subsequently, Rqt2-4 factors target these hybrid state ribosomes specifically, allowing subsequent RQC reactions.