title: Gene-silencing potency of symmetric and asymmetric lipid-conjugated siRNAs and its correlation with dicer recognition.
abstract: Three types of siRNAs and three types of left-overhang siRNAs (LoRNAs) were synthesized along with their conjugations with palmitic acid (C16) to investigate the correlation between Dicer recognition and gene-silencing potency. The siRNA types were composed of 21-nucleotide (nt), 23-nt, and 25-nt lengths of sense and antisense strands with a 2-nt overhang at each 3'-end. The three LoRNA types were composed of a 21-nt, a 23-nt, and a 25-nt length of sense strand with a 2-nt DNA at the 3'-blunt-end and a 23-nt, a 25-nt, and a 27-nt length of antisense strand with a 2-nt overhang at the 3'-end. Additionally, each of these siRNAs and LoRNAs was modified with a C16 at the 5'- or 3'-end of the sense strand; these were named C16-siRNAs and C16-LoRNAs, respectively. The siRNAs and C16-siRNAs were barely cleaved by Dicer, and their gene-silencing efficacies were not excellent, contrary to our expectations. In contrast, most of the LoRNAs and C16-LoRNAs became substrates of Dicer, and they showed both strong gene-silencing efficacies and high nuclease resistance. Among the LoRNAs, the 25D-C16/27-nt LoRNA, which is composed of a 25-nt sense strand with a 2-nt DNA conjugated with C16 at the 3'-end and a 27-nt antisense strand with a 2-nt overhang at the 3'-end, showed an excellent gene-silencing effect with high cell membrane permeability and strong resistance against nuclease degradation. Additionally, the Lo25D-C16/27RNA excelled in all three aspects, nuclease resistance, cell membrane permeability, and RNAi efficacy, compared with the cholesterol conjugation. We are certain that Lo25D-C16/27RNA can be useful as a new generation of RNAi molecules with which to overcome some of the limitations of RNAi technology.
authors.affiliation: Faculty of Pharmacy, Yasuda Women's University , 6-13-1 Yasuhigashi, Asaminami-ku, Hiroshima 731-0153, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Kubo
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Yanagihara
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Sato
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kondo
authors.forename: Toshio
authors.initials: T
authors.lastname: Seyama
mesh_terms: D000818:Animals; D001483:Base Sequence; D002784:Cholesterol / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism*; D034622:RNA Interference; D016372:RNA, Antisense / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics* / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism*
chemical_list: D016372:RNA, Antisense; D034741:RNA, Small Interfering; D019308:Palmitic Acid; D004247:DNA; D002784:Cholesterol; D043244:Ribonuclease III