A Better Way to Isolate RNA AND Protein From the Same Sample
Ambion's new PARIS™ Kit uses a fast, simple procedure based on Ambion's RNAqueous® technology to isolate both RNA and native protein from the same experimental sample. The kit also permits separation of nuclear and cytoplasmic fractions prior to RNA and/or protein isolation. The resulting protein and RNA samples are suitable for various downstream applications, reducing time, cost, and variability between independent experimental samples.
Protein And RNA Isolation System (PARIS)
Figure 1. Schematic of PARIS Procedure.
Using PARIS, RNA and protein can be isolated simultaneously from whole cell lysates. Alternatively, RNA and protein can be isolated from separate nuclear and cytoplasmic fractions (see "Application: Nuclear vs. Cytoplasmic Fractionation" at right). Tissue or cultured cells are first homogenized in ice-cold Cell Disruption Buffer to prepare a total cell lysate. Since the homogenization is performed quickly on ice and in the presence of detergent, both protein and RNA can be purified directly from this lysate. For RNA isolation, a part of the total cell lysate is immediately mixed with an equal volume of Lysis/Binding Solution. This solution contains a high concentration of guanidinium thiocyanate, a strong chaotropic denaturant that rapidly inactivates cellular ribonucleases. Total RNA is then purified from the mixture using an RNA binding glass fiber filter. After three rapid washing steps, high quality RNA is eluted in a concentrated form. The entire procedure can be completed in less than 20 minutes. Note: This kit is not recommended for tissues with high levels of ribonucleases, such as pancreas.
Compatible with Most Downstream Applications
Each protein fraction can also be used directly for most common applications, including functional assays, immunoprecipitation, Western blotting or two-dimensional gel electrophoresis (Figure 2 below). For experiments such as gel shift assays or enzymatic assays, protein samples are usually concentrated enough to be diluted in the final reaction buffer. The Cell Disruption Buffer and Cell Fractionation Buffer have been specially designed to be compatible with downstream analyses.
The PARIS Kit includes sufficient reagent to perform 50 purifications. The kit also comes with a comprehensive Instruction Manual and RNase-free microfuge tubes, glass fiber filters and reagents for RNA isolation. Each purification can accommodate 1 to 75 mg of tissue or 100 to 107 cells.
PARIS is Compatible with RNAlater® and RNAlater-ICE Treated Tissue.
Many researchers use the RNA stabilization reagent RNAlater to protect RNA integrity immediately after cell or tissue collection, to stabilize RNA during long period of storage, or to circumvent the need to grind frozen tissue into a powder prior to RNA isolation. (See the article "RNArticles: Keeping RNA Intact Prior to RNA Isolation - RNAlater®" for some of its many applications.) Ambion's new RNAlater-ICE permits transition of previously frozen samples to a state compatible with handling at room temperature and standard homogenization methods. As shown in Figure 3, the PARIS procedure is compatible with both of these tissue collection/RNA stabilization reagents for both cells and tissue. After homogenization, protein samples are readily available for applications that do not require native functional protein, such as Western blot analysis.
Figure 2. 2D Analysis of Proteins Isolated Using the PARIS Kit. Protein samples were resolved using a pH 4-7 IPG gel followed by 8-16% SDS-PAGE. Top: Total protein (~25 µg) from HeLa cells stained with SYPRO® Ruby. Bottom: Total protein (~125 µg) from mouse brain stained with Coomassie Blue.
Figure 3. RNA and Protein Isolation from Stabilized Samples. (A) Isolation from ~30 mg of mouse liver, brain or kidney 5 days after collection. Samples were either kept frozen at -80ºC, stored in RNAlater® at 4ºC, or snap frozen and then stored in RNAlater-ICE at -20ºC. (B) Isolation from 106 HeLa cells freshly harvested, kept 2 days in RNAlater at RT, or in RNAlater-ICE at -20°C.
Figure 4. Analysis of the RNAi Effect. (A) 5 x 104 HeLa cells were transfected in a 24 well plate with the indicated plasmids. 48 hours after transfection, total RNA and protein were isolated with the PARIS Kit and analyzed by denaturing agarose gel electrophoresis, Northern blot, or Western blot. SCR represents a scrambled siRNA sequence. (B) 5 x 105 Schneider's Drosophila cells were treated for 48 hours in a 6 well plate with 10 nM of the indicated dsRNA prepared with Ambion's MEGAscript® RNAi Kit. Total RNA and protein were isolated with the PARIS Kit and analyzed by Northern blot and Western blot.
Figure 5. Efficient Cellular Fractionation. (A) RNA and protein were isolated from 106 HeLa cells using the PARIS Kit. To allow direct comparison between RNA isolated from different cellular compartments, the same volume of each fraction (~5%) was analyzed by denaturing agarose gel electrophoresis, Northern blot, or Western blot. (B) 3 x 105 HeLa cells were transfected in duplicate in 6 well plates with 1 µg of luciferase mRNA and the relative luciferase activity in each protein fraction was measure 18 hours after transfection. Luciferase mRNA was prepared with Ambion's mMESSAGE mMACHINE® and Poly(A) Tailing Kits.