16242 2016 eng p3103-3112 12 16 article 1 2018-06-01 -- -- The Ribosome Cooperates with the Assembly Chaperone pICln to Initiate Formation of snRNPs The formation of macromolecular complexes within the crowded environment of cells often requires aid from assembly chaperones. PRMT5 and SMN complexes mediate this task for the assembly of the common core of pre-mRNA processing small nuclear ribonucleoprotein particles (snRNPs). Core formation is initiated by the PRMT5-complex subunit pICln, which pre-arranges the core proteins into spatial positions occupied in the assembled snRNP. The SMN complex then accepts these pICln-bound proteins and unites them with small nuclear RNA (snRNA). Here, we have analyzed how newly synthesized snRNP proteins are channeled into the assembly pathway to evade mis-assembly. We show that they initially remain bound to the ribosome near the polypeptide exit tunnel and dissociate upon association with pICln. Coincident with its release activity, pICln ensures the formation of cognate heterooligomers and their chaperoned guidance into the assembly pathway. Our study identifies the ribosomal quality control hub as a site where chaperone-mediated assembly of macromolecular complexes can be initiated. Cell Reports 10.1016/j.celrep.2016.08.047 urn:nbn:de:bvb:20-opus-162420 Cell Reports 16 (2016), 3103–3112. doi: 10.1016/j.celrep.2016.08.047 CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International Elham Paknia Ashwin Chari Holger Stark Utz Fischer eng uncontrolled ribosome eng uncontrolled snRNPs eng uncontrolled assembly chaperone eng uncontrolled pICln Biochemie open_access Lehrstuhl für Biochemie Universität Würzburg https://opus.bibliothek.uni-wuerzburg.de/files/16242/Paknia_CellReports_2016.pdf