[Silencing of c-myc gene expression by enzymatically and chemically synthesized siRNAs]

Small interfering RNAs (siRNA) provide a powerful approach for sequence-specific silencing of gene expression. In the present study we investigated inhibition of c-myc gene expression by siRNAs targeted to the sequence 1452-1470 b. in third exon of c-myc mRNA and to homologous regions in second exons of c-myc (697-715 b.) and N-myc (302-320 b.) mRNAs. siRNAs were prepared enzymatically according to the scheme, including dsDNA-templates preparation using Klenow fragment, separate in vitro transcription of each RNA strand with subsequent hybridization and removal of leader sequences by T1 RNase. Investigation of c-myc gene silencing by siRNAs revealed that enzymatically prepared siRNAs induce stronger inhibition of c-myc expression, than siRNA with the same sequence prepared by chemical synthesis. It was found that down-regulation of c-myc gene expression by investigated siRNAs results in efficient inhibition and even complete arrest of carcinoma cell proliferation, moreover, the extend of growth inhibition correlates with the level of siRNA-mediated reduction of c-myc mRNA.