O ribossomo, além de produzir proteínas, é inspetor de qualidade: mero acaso, fortuita necessidade ou design inteligente?

quinta-feira, outubro 06, 2016

Cell Reports

Volume 16, Issue 12, p 3103–3112, 20 September 2016

The Ribosome Cooperates with the Assembly Chaperone pICln to Initiate Formation of snRNPs

Elham Paknia, Ashwin Chari, Holger Stark, Utz Fischer 4

4Lead Contact

Open Access

Graphical Abstract


• Assembly of macromolecular complexes is initiated at ribosomes

• The assembly chaperone pICln links translation and snRNP assembly

• Ribosomal quality control for the formation of RNA-protein complexes is discovered


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.

Keywords: snRNPs, assembly chaperone, ribosome, pICln

Received: May 11, 2016; Received in revised form: July 11, 2016; Accepted: August 15, 2016; Published: September 20, 2016

© 2016 The Author(s). Published by Elsevier Inc.