Gemin5-dependent RNA association with polysomes enables selective translation of ribosomal and histone mRNAs

Abstract

Selective translation allows to orchestrate the expression of specific proteins in response to different signals through the concerted action of cis-acting elements and RNA-binding proteins (RBPs). Gemin5 is a ubiquitous RBP involved in snRNP assembly. In addition, Gemin5 regulates translation of different mRNAs through apparently opposite mechanisms of action. Here, we investigated the differential function of Gemin5 in translation by identifying at a genome-wide scale the mRNAs associated with polysomes. Among the mRNAs showing Gemin5-dependent enrichment in polysomal fractions, we identified a selective enhancement of specific transcripts. Comparison of the targets previously identified by CLIP methodologies with the polysome-associated transcripts revealed that only a fraction of the targets was enriched in polysomes. Two different subsets of these mRNAs carry unique cis-acting regulatory elements, the 5’ terminal oligopyrimidine tracts (5’TOP) and the histone stem-loop (hSL) structure at the 3’ end, respectively, encoding ribosomal proteins and histones. RNA-immunoprecipitation (RIP) showed that ribosomal and histone mRNAs coprecipitate with Gemin5. Furthermore, disruption of the TOP motif impaired Gemin5-RNA interaction, and functional analysis showed that Gemin5 stimulates translation of mRNA reporters bearing an intact TOP motif. Likewise, Gemin5 enhanced hSL-dependent mRNA translation. Thus, Gemin5 promotes polysome association of only a subset of its targets, and as a consequence, it favors translation of the ribosomal and the histone mRNAs. Together, the results presented here unveil Gemin5 as a novel translation regulator of mRNA subsets encoding proteins involved in fundamental cellular processes.

Phosphorylation of T897 in the dimerization domain of Gemin5 modulates protein interactions and translation regulation

“…Both, RBS1 and RBS2 have been related to translation regulation using different mRNA reporters [10] , [19] . A further link between Gemin5 and translation regulation is supported by recent data showing that silencing of Gemin5 in human cells results in a marked differential association of mRNAs to polysomes, demonstrating that altered levels of this protein regulate the expression of mRNAs encoding proteins with a pivotal role in cell growth, such as ribosomal proteins and histones [68] .…”

Oligomerization regulates the interaction of Gemin5 with members of the SMN complex and the translation machinery

“…S7C ), and histone stem-loop sequence (luc-hSL) at the 3′end (Supplementary Fig. S7D ) [ 23 ]. The results revealed that the oligomerization-proficient protein (G5 845–1508 ) upregulates translation relative to control cells, while the oligomerization-deficient (G5 845–1508 AxE) loses this effect (Supplementary Fig.…”

“…S4B ). Additional functions of Gemin5 such as its potential contribution to assemble diverse type of cellular condensates can be deduced from its dual capacity to interact with various RNAs and multiple RBPs [ 21 , 23 , 40 , 43 ]. This property combined with the oligomerization capacity could facilitate a specific role of Gemin5 in the assembly of distinct ribonucleoprotein complexes, as already reported for translation regulation and spliceosome assembly (Fig.…”

“…HEK293 cells were transfected with the plasmid pCAP-luc [ 67 ] expressing luciferase in a cap-dependent manner and Xpress-His constructs G5 1 – 1508 , or G5 1–739 . For selective translation assays, cells were transfected with the plasmid harboring the TOP sequence (L32 WT TOP) at the 5′end, or the luc-hSL at the 3′end [ 23 ], and those expressing G5 845–1508 or G5 845–1508 AxE [ 38 ]. Cell lysates were prepared 24 hpt in 100 μl lysis buffer (50 mM Tris-HCl pH 7.8, 100 mM NaCl, 0.5% NP40).…”

The SMN-ribosome interplay: a new opportunity for Spinal Muscular Atrophy therapies

“…An intriguing link between the primary function of SMN in the formation of Gemin granules involved in snRNPs biogenesis [ 5–7 ], and its direct role in translation may be attributed to Gemin5. Recognized as an RNA-binding protein (RBP) [ 54 ], Gemin5 takes part in snRNP assembly [ 55 , 56 ], and additionally regulates translation by associating with ribosomes in polysomes [ 38 , 57 ] through mRNAs bearing specific RNA features [ 57 ]. These findings suggest that the interaction between Gemin5 and ribosomes is likely RNA-dependent, raising the possibility that SMN might mediate this interaction.…”