Inducible microRNA expression by an all-in-one episomal vector system

Here we describe an episomal, one-vector system which allows the generation of cell populations displaying homogenous, inducible gene inactivation by RNA interference in a one step procedure. A dual tet-repressor/activator system tightly controls a bi-directional promoter, which simultaneously drives expression of microRNAs and a fluorescent marker protein. We demonstrate the effectiveness of this vector by knockdown of p53 expression in a human cell line which resulted in the expected loss of G₁-arrest after DNA damage. The generation of a cell pool homogenously expressing the ectopic microRNAs was achieved in 1 week without the need for viral infections. Induction of microRNA expression did not elicit an interferon response. Furthermore, the vector was adapted for convenient ligation-free transfer of microRNA cassettes from public libraries. This conditional knockdown-system should prove useful for many research and gene therapeutic applications.     

Highly efficient site-directed RNA cleavage by imidazole-containing conjugates of antisense oligonucleotides

A method has been suggested for the synthesis of conjugates of oligodeoxyribonucleotides with chemical constructs mimicking ribonuclease A active center for directed fragmentation of RNA. The method is based on the sequential addition of linker group, 9-(methylamino)anthracene, to 5' or 3' terminal phosphate of oligonucleotide and then imidazole-containing construct by cycloaddition reaction. The conjugates of oligonucleotides complementary to regions 44-61 (2B-R) and 60-76 (1C-R) of yeast phenylalanine tRNA demonstrated ability to cleave tRNA(Phe) under physiological conditions preferably at the sole phosphodiester bond (C63-A64 for 2B-R and C56-G57 for 1C-R, respectively). The half-time of tRNA(Phe) hydrolysis in the presence of 2B-R conjugate was 30 min at 2B-R concentration of 10 microM and several minutes at conjugate concentration of 50 microM.     

Highly Efficient Site-Directed RNA Cleavage by Imidazole-Containing Conjugates of Antisense Oligonucleotides

A method has been suggested for the synthesis of conjugates of oligodeoxyribonucleotides with chemical constructs mimicking the ribonuclease A active center for directed fragmentation of RNA. The method is based on sequential addition of a linker group, 9-(methylamino)anthracene, to the 5"- or 3"-terminal phosphate of oligonucleotide, and then an imidazole-containing construct by cycloaddition. The conjugates of oligonucleotides complementary to regions 44–61 (2B–R) and 60–76 (1C–R) of yeast phenylalanine tRNA proved able to cleave tRNA^Phe under physiological conditions preferentially at the sole phosphodiester bond (C63–A64 for 2B–R and C56–G57 for 1C–R, respectively). The half-time of tRNA^Phe hydrolysis in the presence of 2B–R conjugate was 30 min at a 2B–R concentration of 10 M and several minutes at conjugate concentration of 50 M.