Chimeric DNA methyltransferases target DNA methylation to specific DNA sequences and repress expression of target genes.

Gene silencing by targeted DNA methylation has potential applications in basic research and therapy. To establish targeted methylation in human cell lines, the catalytic domains (CDs) of mouse Dnmt3a and Dnmt3b DNA methyltransferases (MTases) were fused to different DNA binding domains (DBD) of GAL4 and an engineered Cys2His2 zinc finger domain. We demonstrated that (i) Dense DNA methylation can be targeted to specific regions in gene promoters using chimeric DNA MTases.

Knockdown of hepatic ABCA1 by RNA interference decreases plasma HDL cholesterol levels and influences postprandial lipemia in mice.

Objective: To investigate the impact of hepatic ABCA1 on systemic lipoprotein metabolism in vivo by an adenovirus-mediated RNA interference approach.

Methods And Results: Efficiency of plasmid-based small interference RNA (siRNA)-induced knockdown of cotransfected murine ATP binding cassette transporter A1 (mABCA1) in HEK-293 cells was judged by RT-polymerase chain reaction, immunofluorescence, and Western blot analysis. The most effective plasmid was used to generate a recombinant adenovirus as a tool to selectively downregulate ABCA1 expression in mouse liver (C57BL/6).

Differential RNA interference: replacement of endogenous with recombinant low density lipoprotein receptor-related protein (LRP).

The interpretation of experiments involving the overexpression of a recombinant cDNA is often hampered by the interference of mRNA expression from the endogenous gene locus. Unless cell lines from naturally occurring mutations or knockout mice are available, difficult and time-consuming gene targeting techniques are required to inhibit endogenous gene expression. Using a method we refer to as "differential RNA interference" we demonstrate that RNA interference can be used to selectively suppress endogenous gene expression without affecting the expression of a co-transfected recombinant version of the same protein.