Loss of the ribosomal RNA methyltransferase NSUN5 impairs global protein synthesis and normal growth.

Clemens Heissenberger,Stefan Vogt,Martin Koš,Fabian Nagelreiter,Yulia Gonskikh,Johannes Grillari,Viktoria Ehret,Markus Schosserer,Ina Poser,Emilio Siena,Lisa Liendl,Gerhard Sekot,Eva Harreither,Norbert Polacek,Angela Linder,Teresa L Krammer ,Thomas H Helbich ,Regina Grillari‐Voglauer ,Guo‐Huan Yang ,Pidder Jansen‐Dürr ,Lucia Mičutková ,David P Kreil ,Ernst H K Stelzer

doi:10.1093/nar/gkz1043

Abstract

Modifications of ribosomal RNA expand the nucleotide repertoire and thereby contribute to ribosome heterogeneity and translational regulation of gene expression. One particular m5C modification of 25S ribosomal RNA, which is introduced by Rcm1p, was previously shown to modulate stress responses and lifespan in yeast and other small organisms. Here, we report that NSUN5 is the functional orthologue of Rcm1p, introducing m5C3782 into human and m5C3438 into mouse 28S ribosomal RNA. Haploinsufficiency of the NSUN5 gene in fibroblasts from William Beuren syndrome patients causes partial loss of this modification. The N-terminal domain of NSUN5 is required for targeting to nucleoli, while two evolutionary highly conserved cysteines mediate catalysis. Phenotypic consequences of NSUN5 deficiency in mammalian cells include decreased proliferation and size, which can be attributed to a reduction in total protein synthesis by altered ribosomes. Strikingly, Nsun5 knockout in mice causes decreased body weight and lean mass without alterations in food intake, as well as a trend towards reduced protein synthesis in several tissues. Together, our findings emphasize the importance of single RNA modifications for ribosome function and normal cellular and organismal physiology.

Highlights

Control of cell size and proliferation are integral, but clearly separated processes with many underlying mechanisms remaining unexplained
Evolutionary conservation was highest in the catalytic region, which contains the S-adenosyl methionine (SAM)-binding pocket and cysteines at positions C308 and C359, which are considered to be required for covalent binding and release of the RNA substrate in other RNA methyltransferases [12,32,33]
We here report that loss of NSUN5 induces growth phenotypes in mice and different mammalian cells, which is likely connected to the requirement of NSUN5 for ribosomal RNA modification and normal global protein translation, especially in highly proliferative cells

Summary

Introduction

Control of cell size and proliferation are integral, but clearly separated processes with many underlying mechanisms remaining unexplained. Our current understanding is that both intrinsic developmental programs and extracellular signals control cell number and cell size [1], contributing to growth of whole organisms [2]. Extracellular signals, such as genome size, metabolism, or nutrient availability and -uptake, impinge on important cellular signalling hubs such as the mTOR pathway [3] or the transcription factor Myc [4] that simultaneously control various anabolic processes. This heterogeneity can be generated by changes in stoichiometry and modification patterns of any of the ∼80 core ribosomal proteins (RPs), or their

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