Search Results (3)

Background: Aminoacyl-tRNA synthetases (ARSs) are a group of enzymes responsible for the first step of protein translation. Among them, the KARS1 gene encodes lysyl-tRNA synthetase 1, an enzyme essential for charging tRNA-Lys with lysine in both the cytoplasm and mitochondria. Mutations in KARS1 are associated with a wide range of clinical phenotypes, including leukoencephalopathy, hereditary deafness, peripheral neuropathies, and multisystemic involvement. Methods: We hereby report a detailed case study of a 15-month-old boy presenting at age 5 months with developmental delay, microcephaly, hypotonia, sensorineural deafness, retinopathy, visual impairment, nystagmoid eye movements, and hepatic and immuno-hematological abnormalities. In addition, he exhibited a severe hyperkinetic movement disorder, not previously reported in the literature, and developed epilepsy at 13 months. Genetic testing identified two rare compound heterozygous variants in the KARS1 gene. Results: With this report, we aim to contribute to the expanding of both the clinical phenotype and the allelic spectrum of lysyl-tRNA synthetase-related disorders. Our study also includes a review of previously described KARS1 cases presenting with movement disorders. Conclusions: Our findings further highlight the importance of assessing systemic involvement and performing brain and spinal neuroimaging, as well as implementing genetic screening, in infants presenting with global developmental delay, sensory deficits, and movement disorders—features that may suggest a mitochondrial disorder such as those involving ARS mutations. Full article

Replication of human immunodeficiency virus type 1 (HIV-1) requires the packaging of tRNA^Lys,3 from the host cell into the new viral particles. The GagPol viral polyprotein precursor associates with mitochondrial lysyl-tRNA synthetase (mLysRS) in a complex with tRNA^Lys, an essential step to initiate reverse transcription in the virions. The C-terminal integrase moiety of GagPol is essential for its association with mLysRS. We show that integrases from HIV-1 and HIV-2 bind mLysRS with the same efficiency. In this work, we have undertaken to probe the three-dimensional (3D) architecture of the complex of integrase with mLysRS. We first established that the C-terminal domain (CTD) of integrase is the major interacting domain with mLysRS. Using the pBpa-photo crosslinking approach, inter-protein cross-links were observed involving amino acid residues located at the surface of the catalytic domain of mLysRS and of the CTD of integrase. In parallel, using molecular docking simulation, a single structural model of complex was found to outscore other alternative conformations. Consistent with crosslinking experiments, this structural model was further probed experimentally. Five compensatory mutations in the two partners were successfully designed which supports the validity of the model. The complex highlights that binding of integrase could stabilize the tRNA^Lys:mLysRS interaction. Full article

In yeast Saccharomyces cerevisiae, ~3% of the lysine transfer RNA acceptor 1 (tRK1) pool is imported into mitochondria while the second isoacceptor, tRK2, fully remains in the cytosol. The mitochondrial function of tRK1 is suggested to boost mitochondrial translation under stress conditions. Strikingly, yeast tRK1 can also be imported into human mitochondria in vivo, and can thus be potentially used as a vector to address RNAs with therapeutic anti-replicative capacity into mitochondria of sick cells. Better understanding of the targeting mechanism in yeast and human is thus critical. Mitochondrial import of tRK1 in yeast proceeds first through a drastic conformational rearrangement of tRK1 induced by enolase 2, which carries this freight to the mitochondrial pre-lysyl-tRNA synthetase (preMSK). The latter may cross the mitochondrial membranes to reach the matrix where imported tRK1 could be used by the mitochondrial translation apparatus. This work focuses on the characterization of the complex that tRK1 forms with human enolases and their role on the interaction between tRK1 and human pre-lysyl-tRNA synthetase (preKARS2). Full article