Abstract
The Escherichia coli oligoribonuclease, ORN, has a 3′ to 5′ exonuclease activity specific for small oligomers that is essential for cell viability. The human homologue, REXO2, has hitherto been incompletely characterized, with only its in vitro ability to degrade small single-stranded RNA and DNA fragments documented. Here we show that the human enzyme has clear dual cellular localization being present both in cytosolic and mitochondrial fractions. Interestingly, the mitochondrial form localizes to both the intermembrane space and the matrix. Depletion of REXO2 by RNA interference causes a strong morphological phenotype in human cells, which show a disorganized network of punctate and granular mitochondria. Lack of REXO2 protein also causes a substantial decrease of mitochondrial nucleic acid content and impaired de novo mitochondrial protein synthesis. Our data constitute the first in vivo evidence for an oligoribonuclease activity in human mitochondria.
Highlights
Ribonucleases are enzymes capable of cleaving the phosphodiester bonds between the nucleotide subunits of RNA molecules
Proteinase K treatment of mitochondria (Figure 1B, lane 3) confirmed that REXO2 is within mitochondria and not associated with the outer membrane
Correct maintenance of mitochondrial RNA level is crucial for organellar metabolism
Summary
Ribonucleases are enzymes capable of cleaving the phosphodiester bonds between the nucleotide subunits of RNA molecules. Both endo- and exoribonucleases play important roles in the regulation of RNA levels, performing functions in both RNA processing and degradation [1]. The largest is the superfamily DnaQlike or DEDD named for the four conserved acidic residues that cluster around the catalytic site of all family members. This distinctive core is essential for binding the divalent metal ions that are required for catalysis [3]. The DnaQ-like domain contains three conserved sequence motifs, namely ExoI, ExoII and ExoIII [4,5], each containing this distinctive core the conservation patterns of the three motifs may vary between different subfamilies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
