The adenosine deaminase acting on RNA (ADAR) enzymes that catalyze the conversion of adenosine to inosine in double-stranded (ds)RNA are evolutionarily conserved and are essential for many biological functions including nervous system function, hematopoiesis, and innate immunity. Initially it was assumed that the wide-ranging biological roles of ADARs are due to inosine in mRNA being read as guanosine by the translational machinery, allowing incomplete RNA editing in a target codon to generate two different proteins from the same primary transcript. In humans, there are approximately seventy-six positions that undergo site-specific editing in tissues at greater than 20% efficiency that result in recoding. Many of these transcripts are expressed in the central nervous system (CNS) and edited by ADAR2. Exploiting mouse genetic models revealed that transgenic mice lacking the gene encoding Adar2 die within 3 weeks of birth. Therefore, the role of ADAR2 in generating protein diversity in the nervous system is clear, but why is ADAR RNA editing activity essential in other biological processes, particularly editing mainly involving ADAR1? ADAR1 edits human transcripts having embedded Alu element inverted repeats (AluIRs), but the link from this activity to innate immunity activation was elusive. Mice lacking the gene encoding Adar1 are embryonically lethal, and a major breakthrough was the discovery that the role of Adar1 in innate immunity is due to its ability to edit such repetitive element inverted repeats which have the ability to form dsRNA in transcripts. The presence of inosine prevents activation of the dsRNA sensor melanoma differentiation-associated protein 5 (Mda5). Thus, inosine helps the cell discriminate self from non-self RNA, acting like a barcode on mRNA. As innate immunity is key to many different biological processes, the basis for this widespread biological role of the ADAR1 enzyme became evident.Our group has been studying ADARs from the outset of research on these enzymes. In this Account, we give a historical perspective, moving from the initial purification of ADAR1 and ADAR2 and cloning of their encoding genes up to the current research focus in the field and what questions still remain to be addressed. We discuss the characterizations of the proteins, their localizations, posttranslational modifications, and dimerization, and how all of these affect their biological activities. Another aspect we explore is the use of mouse and Drosophila genetic models to study ADAR functions and how these were crucial in determining the biological functions of the ADAR proteins. Finally, we describe the severe consequences of rare mutations found in the human genes encoding ADAR1 and ADAR2.

• MeSH
• adenosindeaminasa * genetika   metabolismus   MeSH
• dvouvláknová RNA * genetika   MeSH
• inosin genetika   metabolismus   MeSH
• lidé MeSH
• messenger RNA genetika   MeSH
• myši MeSH
• přirozená imunita MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ADAR1 protein, mouse MeSH Prohlížeč
• adenosindeaminasa * MeSH
• dvouvláknová RNA * MeSH
• inosin MeSH
• messenger RNA MeSH

In kinetoplastid protists, all mitochondrial tRNAs are encoded in the nucleus and imported from the cytoplasm to maintain organellar translation. This also applies to the tryptophanyl tRNA (tRNATrp) encoded by a single-copy nuclear gene, with a CCA anticodon to read UGG codon used in the cytosolic translation. Yet, in the mitochondrion it is unable to decode the UGA codon specifying tryptophan. Following mitochondrial import of tRNATrp, this problem is solved at the RNA level by a single C34 to U34 editing event that creates the UCA anticodon, recognizing UGA. To identify the enzyme responsible for this critical editing activity, we scrutinized the genome of Trypanosoma brucei for putative cytidine deaminases as the most likely candidates. Using RNAi silencing and poisoned primer extension, we have identified a novel deaminase enzyme, named here TbmCDAT for mitochondrial Cytidine Deaminase Acting on tRNA, which is responsible for this organelle-specific activity in T. brucei. The ablation of TbmCDAT led to the downregulation of mitochondrial protein synthesis, supporting its role in decoding the UGA tryptophan codon.

• Klíčová slova
• Mitochondrion, cytidine deaminase, editing, trypanosoma, tryptophanyl tRNA,
• MeSH
• cytidin chemie   genetika   MeSH
• cytidindeaminasa genetika   metabolismus   MeSH
• konformace nukleové kyseliny MeSH
• mitochondrie enzymologie   genetika   MeSH
• RNA mitochondriální analýza   genetika   MeSH
• RNA protozoální analýza   genetika   MeSH
• RNA transferová Trp MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• sekvenční homologie MeSH
• terminační kodon * MeSH
• Trypanosoma brucei brucei genetika   růst a vývoj   metabolismus   MeSH
• uridin chemie   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytidin MeSH
• cytidindeaminasa MeSH
• RNA mitochondriální MeSH
• RNA protozoální MeSH
• RNA transferová Trp MeSH
• terminační kodon * MeSH
• uridin MeSH

Although gene duplications provide genetic backup and allow genomic changes under relaxed selection, they may potentially limit gene flow. When different copies of a duplicated gene are pseudofunctionalized in different genotypes, genetic incompatibilities can arise in their hybrid offspring. Although such cases have been reported after manual crosses, it remains unclear whether they occur in nature and how they affect natural populations. Here, we identified four duplicated-gene based incompatibilities including one previously not reported within an artificial Arabidopsis intercross population. Unexpectedly, however, for each of the genetic incompatibilities we also identified the incompatible alleles in natural populations based on the genomes of 1,135 Arabidopsis accessions published by the 1001 Genomes Project. Using the presence of incompatible allele combinations as phenotypes for GWAS, we mapped genomic regions that included additional gene copies which likely rescue the genetic incompatibility. Reconstructing the geographic origins and evolutionary trajectories of the individual alleles suggested that incompatible alleles frequently coexist, even in geographically closed regions, and that their effects can be overcome by additional gene copies collectively shaping the evolutionary dynamics of duplicated genes during population history.

• Klíčová slova
• HPA, TIM22, duplicated gene, genetic incompatibility, genome-wide association study, loss of function,
• MeSH
• alely MeSH
• Arabidopsis genetika   MeSH
• duplikace genu * MeSH
• fylogeografie MeSH
• reprodukční izolace * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH