title: Inhibition of RNAse A family enzymes prevents degradation and loss of silencing activity of siRNAs in serum.
abstract: Small interfering RNAs (siRNA), RNA duplexes of approximately 21 nucleotides, offer a promising approach to specifically degrade RNAs in target cells by a process termed RNA interference. Insufficient in vivo-stability is a major problem of a systemic application of siRNAs in humans. The present study demonstrated that RNAse A-like RNAses degraded siRNAs in serum. The susceptibility of siRNAs towards degradation in serum was strongly enhanced by local clustering of A/Us within the siRNA sequence, i.e. regions showing low thermal stability, most notably at the ends of the molecule, and by 3'-overhanging bases. Importantly, inhibition of RNAse A family enzymes prevented the degradation and loss of silencing activity of siRNAs in serum. Furthermore, the degradation of siRNAs was considerably faster in human than in mouse serum, suggesting that the degradation of siRNAs by RNAse A family enzymes might be a more challenging problem in a future therapeutic application of siRNAs in humans than in mouse models. Together, the present study indicates that siRNAs are degraded by RNAse A family enzymes in serum and that the kinetics of their degradation in serum depends on their sequence. These findings might be of great importance for a possible future human therapeutic application of siRNAs.
authors.affiliation: Department of Internal Medicine II, University of Saarland, D-66421 Homburg/Saar, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Haupenthal
authors.forename: Christina
authors.initials: C
authors.lastname: Baehr
authors.forename: Simone
authors.initials: S
authors.lastname: Kiermayer
authors.forename: Stefan
authors.initials: S
authors.lastname: Zeuzem
authors.forename: Albrecht
authors.initials: A
authors.lastname: Piiper
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D020868:Gene Silencing / Q000502:physiology*; D006801:Humans; D006868:Hydrolysis; D034741:RNA, Small Interfering / Q000097:blood / Q000502:physiology*; D015203:Reproducibility of Results; D012259:Ribonuclease, Pancreatic / Q000502:physiology*; D014162:Transfection
chemical_list: D017931:DNA Primers; D034741:RNA, Small Interfering; D012259:Ribonuclease, Pancreatic