Sequential Ubiquitination of Ribosomal Protein uS3 Triggers the Degradation of Non-functional 18S rRNA

• Published in: Cell reports (Cambridge) Vol. 26; no. 12; pp. 3400 - 3415.e7
• Main Authors: Sugiyama, Takato, Li, Sihan, Kato, Misaki, Ikeuchi, Ken, Ichimura, Atsushi, Matsuo, Yoshitaka, Inada, Toshifumi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19-03-2019; Elsevier
• Subjects: non-functional rRNA decay; Ribosomal Proteins - genetics; Ribosomal Proteins - metabolism; ribosome ubiquitination; RNA Stability; RNA, Fungal - metabolism; RNA, Ribosomal, 18S - genetics; RNA, Ribosomal, 18S - metabolism; RQT complex; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; sequential ubiquitination; subunit dissociation; Ubiquitination; sequential ubiquitination; RQT complex; non-functional rRNA decay; subunit dissociation; ribosome ubiquitination
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2019.02.067

18S non-functional rRNA decay (NRD) eliminates non-functional 18S rRNA with deleterious mutations in the decoding center. Dissociation of the non-functional 80S ribosome into 40S and 60S subunits is a prerequisite step for degradation of the non-functional 18S rRNA. However, the mechanisms by which the non-functional ribosome is recognized and dissociated into subunits remain elusive. Here, we report that the sequential ubiquitination of non-functional ribosomes is crucial for subunit dissociation. 18S NRD requires Mag2-mediated monoubiquitination followed by Hel2- and Rsp5-mediated K63-linked polyubiquitination of uS3 at the 212th lysine residue. Determination of the aberrant 18S rRNA levels in sucrose gradient fractions revealed that the subunit dissociation of stalled ribosomes requires sequential ubiquitination of uS3 by E3 ligases and ATPase activity of Slh1 (Rqt2), as well as Asc1 and Dom34. We propose that sequential uS3 ubiquitination of the non-functional 80S ribosome induces subunit dissociation by Slh1, leading to degradation of the non-functional 18S rRNA.
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•18S non-functional rRNA decay requires sequential uS3 ubiquitination•Hel2 and Rsp5 form a K63-linked polyubiquitin chain on uS3 monoubiquitinated by Mag2•uS3 ubiquitination induces subunit dissociation of non-functional 80S by Slh1 (Rqt2)
18S non-functional rRNA decay (NRD) eliminates non-functional 18S rRNA with deleterious mutations in the decoding center. Sugiyama et al. show that 18S NRD requires Mag2-mediated monoubiquitination followed by Hel2- and Rsp5-mediated K63-linked polyubiquitination of uS3. Subunit dissociation requires Asc1, Dom34, sequential ubiquitination of uS3, and ATPase activity of Slh1 (Rqt2).