%0 Journal Article
%T Dicer Functions in Aquatic Species
%A Yasuko Kitagishi
%A Naoko Okumura
%A Hitomi Yoshida
%A Chika Tateishi
%A Yuri Nishimura
%A Satoru Matsuda
%J Journal of Amino Acids
%D 2011
%I Hindawi Publishing Corporation
%R 10.4061/2011/782187
%X Dicer is an RNase III enzyme with two catalytic subunits, which catalyzes the cleavage of double-stranded RNA to small interfering RNAs and micro-RNAs, which are mainly involved in invasive nucleic acid defense and endogenous genes regulation. Dicer is abundantly expressed in embryos, indicating the importance of the protein in early embryonic development. In addition, Dicer is thought to be involved in defense mechanism against foreign nucleic acids such as viruses. This paper will mainly focus on the recent progress of Dicer-related research and discuss potential RNA interference pathways in aquatic species. 1. Introduction In eukaryotes, small RNA-mediated RNA silencing called RNA interference (RNAi) is able to suppress gene expression. Dicer is the key enzyme of the RNAi pathway to cleave double-stranded RNA (dsRNA) into small RNAs categorized as small interfering RNAs (siRNAs) or micro-RNAs (miRNAs), which are mainly involved in invasive nucleic acid defense and endogenous genes regulation, respectively [1¨C3]. Then, Dicer is reported to participate in both the antiviral immune response and developmental regulation. For example, Drosophila harboring the Dicer mutant exhibited enhanced disease susceptibility to cricket paralysis virus [4, 5]. In addition, Caenorhabditis elegans harboring the Dicer mutant had developmental phenotype defects [6¨C8]. The meRNAi is a conserved eukaryotic gene silencchanism that works at both the transcriptional and the posttranscriptional levels [9]. We fortuitously cloned and sequenced the human Dicer, (initially designated as HERNA) for the first time [10]. Dicer belongs to the RNase III family with ATP dependent RNA helicase, PAZ (Piwi/Argonaute/Zwille), dsRNA binding, and RNase III domains (Figure 1), which is responsible for cleaving long dsRNAs into siRNAs or miRNAs when associated with other proteins likeR2D2in Drosophila or the transactivating response RNA-binding protein in Homo sapiens to recruiting Argonaute proteins. The PAZ domain binds the single stranded 3¡ä end of small RNA [11], and it might function in protein-protein interaction. Small RNAs includes PIWI-associated RNAs (piRNAs), short single-stranded RNAs arising from a Dicer-independent pathway, which are found in germ cells and associate with the PIWI subfamily of Argonaute proteins [12, 13]. Many zebrafish piRNAs are derived from repetitive sequences. Mutations in the Piwi homologue protein result either in loss of germ cells or in defects in meiosis and chromosome segregation in eggs. However, the Dicer knockout mouse eggs raise a question about
%U http://www.hindawi.com/journals/jaa/2011/782187/