title: SUMO routes ribosome maturation.
abstract: The control of ribosome biogenesis is a critical cellular nodal point, which ensures that protein synthesis is coordinated with cell growth and proliferation. Prior to their cytoplasmic assembly the 40S and 60S ribosomal subunits pass through the nucleolus and the nucleoplasm via a maturation pathway that involves a set of non-coding RNAs and non-ribosomal regulatory trans-acting factors. In mammalian cells the inventory of the required protein components is still fragmentary and it is largely unclear what drives the subcellular transitions and the exchange of protein components along the maturation pathway. However, recent data indicate that the dynamic post-translational modification by the ubiquitin-like SUMO modifier is critically involved in these processes. In particular, removal of SUMO from trans-acting factors by the SUMO-specific isopeptidase SENP3 is instrumental in the 60S maturation pathway in mammals. In an attempt to pinpoint the relevant targets of SENP3 we identified a novel SENP3-associated protein complex comprised of PELP1, TEX10 and WDR18. We demonstrated that this complex is involved in the nucleolar steps of 28S rRNA maturation and the subsequent nucleoplasmic transit of the 60S ribosomal subunit. Importantly, we found that PELP1 is a SENP3-sensitive target of SUMO and observed that lack of SENP3-mediated desumoylation prevents the nucleolar partitioning of the PELP1-TEX10-WDR18 complex. SUMO-dependent subnuclear trafficking may thus assist in coordinating the rate of ribosome formation. Here we propose that sumoylation of PELP1 serves as a quality control mechanism that restricts pre-mature loading of the PELP1-WDR18-TEX10 complex to 60S particles thereby limiting ribosome maturation. We further hypothesize that the PELP1-associated AAA-ATPase MDN1 may be part of this surveillance pathway.
authors: Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors: Elisabeth
authors: E
authors: Finkbeiner
authors: Markus
authors: M
authors: Haindl
authors: Nithya
authors: N
authors: Raman
authors: Stefan
authors: S
authors: Muller
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism; D056970:Co-Repressor Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D012339:RNA, Ribosomal, 28S / Q000235:genetics / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000235:genetics / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D058207:Sumoylation / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D056970:Co-Repressor Proteins; C438485:PELP1 protein, human; D012339:RNA, Ribosomal, 28S; D025841:Small Ubiquitin-Related Modifier Proteins; D014157:Transcription Factors; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C503949:MDN1 protein, human; D000074183:ATPases Associated with Diverse Cellular Activities