Arabidopsis thaliana endonuclease V is a ribonuclease specific for inosine-containing single-stranded RNA |
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Authors: | Megumi Endo Jung In Kim Narumi Aoki Shioi Shigenori Iwai Isao Kuraoka |
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Institution: | 1. Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan ; 2. Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan |
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Abstract: | Endonuclease V is highly conserved, both structurally and functionally, from bacteria to humans, and it cleaves the deoxyinosine-containing double-stranded DNA in Escherichia coli, whereas in Homo sapiens it catalyses the inosine-containing single-stranded RNA. Thus, deoxyinosine and inosine are unexpectedly produced by the deamination reactions of adenine in DNA and RNA, respectively. Moreover, adenosine-to-inosine (A-to-I) RNA editing is carried out by adenosine deaminase acting on dsRNA (ADARs). We focused on Arabidopsis thaliana endonuclease V (AtEndoV) activity exhibiting variations in DNA or RNA substrate specificities. Since no ADAR was observed for A-to-I editing in A. thaliana, the possibility of inosine generation by A-to-I editing can be ruled out. Purified AtEndoV protein cleaved the second and third phosphodiester bonds, 3′ to inosine in single-strand RNA, at a low reaction temperature of 20–25°C, whereas the AtEndoV (Y100A) protein bearing a mutation in substrate recognition sites did not cleave these bonds. Furthermore, AtEndoV, similar to human EndoV, prefers RNA substrates over DNA substrates, and it could not cleave the inosine-containing double-stranded RNA. Thus, we propose the possibility that AtEndoV functions as an RNA substrate containing inosine induced by RNA damage, and not by A-to-I RNA editing in vivo. |
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Keywords: | endonuclease V inosine Arabidopsis thaliana RNA damage RNA editing |
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