Proteasomal degradation of human release factor eRF3a regulates translation termination complex formation

Abstract

In eukaryotes, eRF1 and eRF3 are associated in a complex that mediates translation termination. The regulation of the formation of this complex in vivo is far from being understood. In mammalian cells, depletion of eRF3a causes a reduction of eRF1 level by decreasing its stability. Here, we investigate the status of eRF3a when not associated with eRF1. We show that eRF3a forms altered in their eRF1-binding site have a decreased stability, which increases upon cell treatment with the proteasome inhibitor MG132. We also show that eRF3a forms altered in eRF1 binding as well as wild-type eRF3a are polyubiquitinated. These results indicate that eRF3a is degraded by the proteasome when not associated with eRF1 and suggest that proteasomal degradation of eRF3a controls translation termination complex formation by adjusting the eRF3a level to that of eRF1.

A role for the proteasome in the turnover of Sup35p and in [PSI+] prion propagation

“…We and others have found that Sup35p is a very stable protein with an estimated half‐life (> 2 h) that is longer than a typical yeast cell division cycle in rich medium (∼ 90 min). In agreement with these observations, a human orthologue of Sup35p (eRF3a) was also shown to have a very long half‐life (> 30 h), which may in part be due to its stable interaction with eRF1 within the translation termination complex (Chauvin and Jean‐Jean, ). Whether the interaction between Sup35p and Sup45p, the yeast eRF1 orthologue, contributes to the stability of these proteins is unknown but suggested by previous studies (Valouev et al ., ).…”

“…Whether the interaction between Sup35p and Sup45p, the yeast eRF1 orthologue, contributes to the stability of these proteins is unknown but suggested by previous studies (Valouev et al ., ). The degradation of human eRF3a was shown to be dependent on proteasomal activity (Chauvin and Jean‐Jean, ), yet a conclusive proof that this degradation required eRF3a to be ubiquitinated is still lacking. Because of the extended stability of Sup35p, cycloheximide‐chase experiments in the presence or absence of proteasome inhibitors were not the appropriate approach to investigate the involvement of the proteasome in Sup35p turnover.…”

Studies on human eRF3-PABP interaction reveal the influence of eRF3a N-terminal glycin repeat on eRF3-PABP binding affinity and the lower affinity of eRF3a 12-GGC allele involved in cancer susceptibility

“… 17,18 eRF3a is the major form of eRF3 in the majority of the tissues and its abundance regulates the formation of translation termination complex. 19,20 eRF3b, which can complement eRF3a for its role in translation termination, is very poorly expressed in most tissues and likely does not play a major role in termination. 20 eRF3a and eRF3b proteins differ in their N-terminal domain.…”

Genetic association and functional characterization of MCPH1 gene variation in bipolar disorder and schizophrenia

“…The results from the GeneMANIA analyses of genes whose expression was altered by rs61749465 identified nine genes that were co expressed with MCPH1 (Supporting Information Table S4). These genes have been shown to be involved in: stimulating cell proliferation/migration (S TIP1 and EGFL7 ; Chao et al, ; Yang et al, ); cell proliferation and cancer development ( ZFR ) (Zhao, Chen, & Tan, ); axon guidance and in the development of peripheral and central nervous system ( SEMA6B ; Chao et al, ; Collet et al, ); cellular metabolism by regulating nucleic acid aggregation ( SFPQ ) (Lee et al, ); translation elongation and neuronal process extension and survival ( EIF5A ; Huang, Higginson, Hester, Park, & Snyder, ); control of translation termination ( GSPT1 ; Chauvin & Jean‐Jean, ); the regulation of development and maintenance of stem cells ( CTR9 ; Nagaike et al, ). GeneMANIA analysis for genes whose expression was altered by rs199422124 included two genes Desmocollin 3 ( DSC3 ) and Cadherin 13 ( CDH13 ) that were co expressed with MCPH1.…”