mRNA Purification

 I. Prepare oligo-dT cellulose

• use 40 mg oligo-dT cellulose / 1 mg total RNA
• swell oligo dT-cellulose in elution buffer
• wash oligo dT-cellulose 4 x with elution buffer (30 sec. full speed spin in between)
• equilibrate oligo-dT cellulose with 2 to 3 washing steps using 1x binding buffer

 II. mRNA purification

• bring 1 mg total RNA with H₂O to 600 µl
• incubate 4 min at 65 °C
• add 600 µl 2x binding buffer
• add to 40 mg 1x binding buffer equilibrated oligo-dT cellulose
• incubate 15 min at RT on a rolling incubator or vortex several times in between
• spin oligo-dT cellulose down, discard supernatant
• wash 2 x with 1x binding buffer
• wash 2 x with wash buffer
• elute with 250 µl elution buffer at 37 °C for 5 min
• spin and keep supernatant (for second round of purification or precipitation)
• elute oligo-dT cellulose again with 250 µl elution buffer
• spin and keep supernatant (for second round of purification or precipitation)
• combine eluate and add H₂O to 600 µl
• repeat mRNA purification by starting again with 4 min incubation at 65 °C

 III. Recover mRNA

• add 50 µl 4 M NaCl and precipitate with 2 vol. cold EtOH
• incubate 1 h at -20 °C
• spin 10 min full speed, wash with 70 % EtOH, air dry and dissolve in 20 µl H₂O
• read A₂₆₀ of 1 µl (100 to 250 fold diluted)
• run 1 µg ( and 10 µg total RNA as comparison) on a 1.2 % agarose Formaldehyde gel
  
  recovery = 1-2 % of the total RNA (10-20 µg mRNA / 2 mg total RNA)
  
  

Buffers:
[all buffers should be made with DEPC treated/autoclaved components!]

 oligo dT cellulose (type7, Pharmacia)

 2 x binding buffer:
1 M NaCl; 20 mM Tris pH 7.5; 2 mM EDTA; 0.1 % SDS
[50 ml: 12.5 ml 4 M NaCl; 1 ml 1 M Tris; 200 µl 0.5 M EDTA; 500 µl 10 % SDS]

 1 x binding buffer:
0.5 M NaCl; 10 mM Tris pH 7.5; 1 mM EDTA; 0.05 % SDS
[50 ml: 6.25 ml 4 M NaCl; 500 µl 1 M Tris; 100 µl 0.5 M EDTA; 250 µl 10 % SDS]

 wash buffer:
0.2 M NaCl; 10 mM Tris pH 7.5; 1 mM EDTA; 0.05 % SDS
[50 ml: 2.5 ml 4 M NaCl; 500 µl 1 M Tris; 100 µl 0.5 M EDTA; 250 µl 10 % SDS]

 elution buffer:
10 mM Tris pH 7.5; 1 mM EDTA; 0.05 % SDS
[50 ml: 500 µl 1 M Tris; 100 µl 0.5 M EDTA; 250 µl 10 % SDS]