Batch Method Protocol (S1560)  for Isolation of mRNA Using the  PolyA Spin™ mRNA Isolation Kit

Protocol

1. Isolation Procedure:
   
   Add 50 μl of 5M NaCl per 450 μl of cell lysate or total RNA solution or dissolve total RNA sample in 450 μl of Elution Buffer then add 50 μl of 5M NaCl. Make sure that sample is totally dissolved. If not, microcentrifuge for 5 minutes to pellet insoluble material. Transfer RNA solution to clean microcentrifuge tube.
   
   
2. Heat at 65°C for 5 minutes and quickly cool in an ice bath for 3 minutes.
   
   For information regarding the preparation of total RNA from eukaryotic cells or tissue see Maniatis, T. et al. (1989). Molecular Cloning: A Laboratory Manual, (2nd ed.) (pp. 7.6–7.25). Cold Spring Harbor.
   
   
3. Apply total RNA solution to equilibrated oligo (dT)₂₅ cellulose, seal cap and mix thoroughly. Let stand at room temperature for 5 minutes agitating by hand or place horizontally on rotary shaker.
   
   
4. Microcentrifuge for 10 seconds.
   
   Note: It is important to agitate beads during binding, washing and elution steps.
   
   
5. Pipet supernant back into original microcentrifuge tube. Repeat steps 2 thru 4.
   
   
6. Pipet supernant back into original microcentrifuge tube for storage. It is recommended that no eluates be discarded until entire isolation procedure is completed and the results are evaluated. Eluates can be stored in sterile test tubes on ice.
   
   
7. Add 400 μl of Wash Buffer to oligo (dT)₂₅ beads, let stand at room temperature for 2 minutes agitating by hand or place horizontally on rotary shaker. Microcentrifuge for 10 seconds, then using a micropipette decant supernant to a clean 13 x 100 mm test tube.
   
   
8. Add 400 μl of Wash Buffer to cellulose beads and wash as in Step 7 three times.
   
   
9. Using the same method wash cellulose beads once with 400 μl of Low Salt Buffer.
   
   *Note: This wash step with 0.1 M NaCl removes residual poly(A)^– RNA that is bound to the cellulose column. This step can be omitted during a second round purification.
   
   
10. Add 200 μl of prewarmed Elution Buffer to cellulose beads. Agitate by hand to resuspend the cellulose beads. Let stand for 2 minutes agitating by hand or place on rotary shaker. Using a 1 ml pipette with sterile tip transfer Elution Buffer and beads to the column reservoir of a clean microcentrifuge spin column unit (provided with kit). Microcentrifuge for 10 seconds.
    
    
11. Add 200 μl fresh prewarmed Elution Buffer to column reservoir. Agitate by hand resuspending the cellulose beads. Let stand for 2 minutes agitating by hand or place on rotary shaker. Microcentrifuge for 10 seconds.
    
    
12. Place Elution Buffer eluate on ice.
    
    At this point quantification of isolated poly(A)⁺ can be done by spectrophotometric measurement at A₂₆₀ nm. This is most easily done in a 0.5 ml quartz cuvette. Soak cuvette for at least one hour in methanol: concentrated HCL (1:1), then rinse copiously with H₂O which has been DEPC treated.
    
    For RNA 1 A₂₆₀ U = approx. 40 μg
    
    If second round purification is to be done immediately, equilibrate fresh oligo (dT)₂₅ cellulose and repeat isolation procedure starting at step 1 of Spin Method Protocol . If poly(A)⁺ eluate is to be used at this point it can be ethanol precipitated:
    
    a) To poly(A)⁺ eluate add 44 μl of 3 M Sodium acetate, 20 μl of glycogen solution and 1.0 ml of cold 95% ethanol. Allow to stand at -20°C for at least 30 minutes.
    
    At this point poly(A)+ material can be stored as an ethanol precipitate at -70°C until it is needed.
    
    To recover poly(A)⁺ material microcentrifuge for 15 minutes at 4°C. Carefully decant supernant, then wash the pellet (often not visible) with 70% ethanol. Recentrifuge briefly, decant supernant and allow pellet to air dry. Resuspend poly(A)⁺ material as required.