Isolation of full-length RNA from a thermophilic cyanobacterium

Isolation of full-length mRNA without degradation is critical in the study of in vivo gene regulation and transcription, cDNA synthesis and reverse transcription (RT)-PCR. It is particularly difficult to isolate full-length mRNA from thermophiles, which have higher turnover rates of mRNA degradation. Mastigocladus laminosus is a thermophilic heterocystous cyanobacterium. The assay of M. laminosus cell lysates showed that RNase activity was high and was resistant to the conventional guanidine thiocyanate and 2-mercaptoethanol denaturation methods. The mRNA isolated by several conventional methods was completely degraded. A method was developed to purify full-length mRNA by a combination of fast cooling, vanadyl-ribonucleoside-complex inhibition, phenol-chloroform-isoamyl alcohol extraction, lithium chloride precipitation and the lysing of cells with the French Press. This method produced high-quality, full-length mRNA in high yield. Purified mRNA was suitable for Northern blotting, cDNA synthesis and RT-PCR. This method could be applicable to other thermophiles in which the RNase activity is high and/or is resistant to guanidine thiocyanate.