title: A Single RNaseIII Domain Protein from Entamoeba histolytica Has dsRNA Cleavage Activity and Can Help Mediate RNAi Gene Silencing in a Heterologous System.
abstract: Dicer enzymes process double-stranded RNA (dsRNA) into small RNAs that target gene silencing through the RNA interference (RNAi) pathway. Dicer enzymes are complex, multi-domain RNaseIII proteins, however structural minimalism of this protein has recently emerged in parasitic and fungal systems. The most minimal Dicer, Saccharomyces castellii Dicer1, has a single RNaseIII domain and two double stranded RNA binding domains. In the protozoan parasite Entamoeba histolytica 27nt small RNAs are abundant and mediate silencing, yet no canonical Dicer enzyme has been identified. Although EhRNaseIII does not exhibit robust dsRNA cleavage in vitro, it can process dsRNA in the RNAi-negative background of Saccharomyces cerevisiae, and in conjunction with S. castellii Argonaute1 can partially reconstitute the RNAi pathway. Thus, although EhRNaseIII lacks the domain architecture of canonical or minimal Dicer enzymes, it has dsRNA processing activity that contributes to gene silencing via RNAi. Our data advance the understanding of small RNA biogenesis in Entamoeba as well as broaden the spectrum of non-canonical Dicer enzymes that contribute to the RNAi pathway.
authors.affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Justine M
authors.initials: JM
authors.lastname: Pompey
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Stanford University School of Medicine, Stanford, California, United States of America; Molecular Genetics and Enzymology Department, National Research Centre, Dokki, Egypt.
authors.forename: Bardees
authors.initials: B
authors.lastname: Foda
authors.affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America; Division of Infectious Diseases, Department of Internal Medicine, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Upinder
authors.initials: U
authors.lastname: Singh
mesh_terms: D004748:Entamoeba histolytica / Q000201:enzymology / Q000235:genetics*; D020868:Gene Silencing / Q000502:physiology*; D017125:Genes, Protozoan / Q000235:genetics / Q000502:physiology; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000502:physiology; D059367:RNA Cleavage / Q000235:genetics* / Q000502:physiology; D034622:RNA Interference / Q000502:physiology*; D012330:RNA, Double-Stranded / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism* / Q000502:physiology; D012440:Saccharomyces / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology
chemical_list: D012330:RNA, Double-Stranded; D043244:Ribonuclease III