Transfer RNAs acquire a large plethora of chemical modifications. Among those, modifications of the anticodon loop play important roles in translational fidelity and tRNA stability. Four human wobble U-containing tRNAs obtain 5-methoxycarbonylmethyluridine (mcm5U34) or 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U34), which play a role in decoding. This mark involves a cascade of enzymatic activities. The last step is mediated by alkylation repair homolog 8 (ALKBH8). In this study, we performed a transcriptome-wide analysis of the repertoire of ALKBH8 RNA targets. Using a combination of HITS-CLIP and RIP-seq analyses, we uncover ALKBH8-bound RNAs. We show that ALKBH8 targets fully processed and CCA modified tRNAs. Our analyses uncovered the previously known set of wobble U-containing tRNAs. In addition, both our approaches revealed ALKBH8 binding to several other types of noncoding RNAs, in particular C/D box snoRNAs.
Frameshifting of mRNA during translation provides a strategy to expand the coding repertoire of cells and viruses. How and where in the elongation cycle +1-frameshifting occurs remains poorly understood. We describe seven ~3.5-Å-resolution cryo-EM structures of 70S ribosome complexes, allowing visualization of elongation and translocation by the GTPase elongation factor G (EF-G). Four structures with a + 1-frameshifting-prone mRNA reveal that frameshifting takes place during translocation of tRNA and mRNA. Prior to EF-G binding, the pre-translocation complex features an in-frame tRNA-mRNA pairing in the A site. In the partially translocated structure with EF-G•GDPCP, the tRNA shifts to the +1-frame near the P site, rendering the freed mRNA base to bulge between the P and E sites and to stack on the 16S rRNA nucleotide G926. The ribosome remains frameshifted in the nearly post-translocation state. Our findings demonstrate that the ribosome and EF-G cooperate to induce +1 frameshifting during tRNA-mRNA translocation.
- MeSH
- biokatalýza MeSH
- elektronová kryomikroskopie MeSH
- elongace translace peptidového řetězce genetika MeSH
- elongační faktor G chemie genetika metabolismus MeSH
- Escherichia coli genetika metabolismus MeSH
- konformace nukleové kyseliny MeSH
- konformace proteinů MeSH
- messenger RNA chemie genetika metabolismus MeSH
- molekulární modely MeSH
- posun čtecího rámce na ribozómech genetika MeSH
- proteiny z Escherichia coli chemie genetika metabolismus MeSH
- ribozomy genetika metabolismus ultrastruktura MeSH
- RNA ribozomální 16S chemie genetika metabolismus MeSH
- RNA transferová chemie genetika metabolismus MeSH
- tRNA-methyltransferasy genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Regulation of cellular iron homeostasis is crucial as both iron excess and deficiency cause hematological and neurodegenerative diseases. Here we show that mice lacking iron-regulatory protein 2 (Irp2), a regulator of cellular iron homeostasis, develop diabetes. Irp2 post-transcriptionally regulates the iron-uptake protein transferrin receptor 1 (TfR1) and the iron-storage protein ferritin, and dysregulation of these proteins due to Irp2 loss causes functional iron deficiency in β cells. This impairs Fe-S cluster biosynthesis, reducing the function of Cdkal1, an Fe-S cluster enzyme that catalyzes methylthiolation of t6A37 in tRNALysUUU to ms2t6A37. As a consequence, lysine codons in proinsulin are misread and proinsulin processing is impaired, reducing insulin content and secretion. Iron normalizes ms2t6A37 and proinsulin lysine incorporation, restoring insulin content and secretion in Irp2-/- β cells. These studies reveal a previously unidentified link between insulin processing and cellular iron deficiency that may have relevance to type 2 diabetes in humans.
- MeSH
- beta-buňky metabolismus MeSH
- homeostáza MeSH
- inzulin metabolismus MeSH
- inzulinom genetika metabolismus MeSH
- krysa rodu rattus MeSH
- myši inbrední C57BL MeSH
- myši knockoutované MeSH
- nádorové buněčné linie MeSH
- nádory slinivky břišní genetika metabolismus MeSH
- porucha glukózové tolerance genetika MeSH
- proinsulin genetika metabolismus MeSH
- proteiny obsahující železo a síru metabolismus MeSH
- regulační protein železa 2 genetika metabolismus MeSH
- RNA transferová Lys genetika metabolismus MeSH
- signální dráha UPR genetika MeSH
- tRNA-methyltransferasy genetika metabolismus MeSH
- železo metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
The nucleolar protein 2 gene encodes a protein specific for the nucleolus. It is assumed that it plays a role in the synthesis of ribosomes and regulation of the cell cycle. Due to its link to cell proliferation, higher expression of Nop2 indicates a worse tumor prognosis. In this work we used Nop2(gt1gaj) gene trap mouse strain. While lethality of homozygous animals suggested a vital role of this gene, heterozygous animals allowed the detection of expression of Nop2 in various tissues, including mouse brain. Histochemistry, immunohistochemistry and immunoelectron microscopy techniques, applied to a mature mouse brain, human brain and on mouse neural stem cells revealed expression of Nop2 in differentiating cells, including astrocytes, as well as in mature neurons. Nop2 was detected in various regions of mouse and human brain, mostly in large pyramidal neurons. In the human, Nop2 was strongly expressed in supragranular and infragranular layers of the somatosensory cortex and in layer III of the cingulate cortex. Also, Nop2 was detected in CA1 and the subiculum of the hippocampus. Subcellular analyses revealed predominant location of Nop2 within the dense fibrillar component of the nucleolus. To test if Nop2 expression correlates to cell proliferation occurring during tissue regeneration, we induced strokes in mice by middle cerebral artery occlusion. Two weeks after stroke, the number of Nop2/nestin double positive cells in the region affected by ischemia and the periventricular zone substantially increased. Our findings suggest a newly discovered role of Nop2 in both mature neurons and in cells possibly involved in the regeneration of nervous tissue.
- MeSH
- astrocyty fyziologie MeSH
- cévní mozková příhoda patofyziologie MeSH
- dospělí MeSH
- infarkt arteria cerebri media MeSH
- jaderné proteiny genetika metabolismus MeSH
- kultivované buňky MeSH
- lidé MeSH
- modely nemocí na zvířatech MeSH
- mozek fyziologie patofyziologie MeSH
- myši inbrední C57BL MeSH
- myši transgenní MeSH
- nervové kmenové buňky fyziologie MeSH
- nestin metabolismus MeSH
- neurogeneze fyziologie MeSH
- neurony fyziologie MeSH
- proliferace buněk fyziologie MeSH
- tRNA-methyltransferasy metabolismus MeSH
- zvířata MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
