Extraction of RNA from cells and tissue

Total undegraded cellular RNA, largely free of contaminating DNA, can be rapidly and easily isolated from homogenized tissue or cultured cells using acid pH guanidinium thiocyanate/phenol/chloroform extraction. Commercially available acid phenol/guanidinium thiocyanate solutions allow one-step complete solubilization of tissue or cells under conditions that inhibit RNAse activity. We describe here a detailed procedure for total RNA extraction from homogenized tissues or cultured cells using such reagents, together with additional purification steps by passage through Phase-Lock gel tubes, and recommend optional chromatographic poly(A+) RNA enrichment procedure using Mini Oligo(dT) spin columns, together with the spectrophotometric determination of RNA yield and purity.