cell line that is considered difficult to transfect using lipid-based reagents. Herein, we present a method for lipid-mediated siRNA transfection of fully differentiated 3T3-L1 Food green 3 biological activity adipocytes and primary human adipocytes that is based on incubating the siRNA/lipid complex with the detached adipocytes in suspension. This results in highly efficient siRNA transfection and is simple, cost-effective, and nontoxic, making this approach well suited to systematic high throughput siRNA screening of fully differentiated adipocytes. When cell viability under the optimized conditions was assayed by the production of calcein from calcein-AM or PI binding to DNA, the overwhelming majority of adipocytes remain viable compared to the dead cells as assayed using fluorescence detection of calcein and DNA bound 1494675-86-3 propidium iodide. This indicates lipid-based siRNA transfection of the adipocytes while in suspension does not adversely affect the viability of fully differentiated adipocytes. The effectiveness of RNAi experiments is determined by the efficiency of siRNA transfection and the ability of the siRNA sequence to silence a specific target mRNA. To test the efficiency of gene knockdown, we assayed the siRNA-mediated decrease in expression of the peroxisome proliferator activated receptor gamma, a nuclear receptor that is required for the formation and maintenance of adipocytes. Along with PPARc as our gene of interest, we also transfected the fully differentiated adipocytes with siRNA directed against lamin A/C as a control target and the luciferase siRNA as a nontargeting control. In addition, we are interested in the role of the ubiquitin proteasome system in regulating PPARc transcriptional activity in adipocytes. Therefore, we also tested the efficiency of knockdown of three ubiquitin ligases that regulate nuclear hormone receptor activity. E6-AP regulates nuclear receptor activity and targets the estrogen receptor alpha to the proteasome for degradation. The TBL-1 and TBLR-1 genes are ubiquitin ligases that target the nuclear receptor corepressor NCoR to the proteasome for degradation. As shown in Figure 5, we obtain efficient knockdown of lamin A/C, PPARc, and E6-AP protei
