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Ribosome stalling induced by mutation of a CNS-specific tRNA causes neurodegeneration

Science  25 Jul 2014:
Vol. 345, Issue 6195, pp. 455-459
DOI: 10.1126/science.1249749

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Problems making proteins kills nerve cells

Neurodegeneration is associated with a variety of different diseases, but its cellular roots are often obscure. Ishimura et al. find that mutant mice whose brain cells start to die rapidly soon after birth have lost the function of two vital cellular components (see the Perspective by Darnell). The first is a protein that releases stalled ribosomes stuck on messenger RNA (mRNA); the second is a transfer RNA (tRNA), which reads the code for arginine in the mRNA. This tRNA is expressed predominantly in the central nervous system. The lack of the tRNA leads to increased ribosomal stalling at arginine codons, which, when left uncorrected, blocks protein synthesis and proves fatal.

Science, this issue p. 455; see also p. 378

Abstract

In higher eukaryotes, transfer RNAs (tRNAs) with the same anticodon are encoded by multiple nuclear genes, and little is known about how mutations in these genes affect translation and cellular homeostasis. Similarly, the surveillance systems that respond to such defects in higher eukaryotes are not clear. Here, we discover that loss of GTPBP2, a novel binding partner of the ribosome recycling protein Pelota, in mice with a mutation in a tRNA gene that is specifically expressed in the central nervous system causes ribosome stalling and widespread neurodegeneration. Our results not only define GTPBP2 as a ribosome rescue factor but also unmask the disease potential of mutations in nuclear-encoded tRNA genes.

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