Polyinosinic acid as a carrier in the microscale purification of total RNA

Three different RNA carriers were compared for use in microscale RNA isolation and subsequent cDNA synthesis and amplification via the polymerase chain reaction. E.coli rRNA alone gave considerable cDNA synthesis which under standard carrier conditions overwhelmed cDNA synthesis from lymphocyte mRNA. Yeast tRNA caused inhibition of mRNA primed cDNA synthesis, giving low levels of cDNA synthesis when used without cellular RNA. In contrast, commercially available poly I alone did not prime detectable cDNA synthesis nor did it inhibit such synthesis primed by cellular mRNA. When RNA preparations were made using these three carriers and decreasing numbers of starting lymphocytes, poly I allowed the detection of cDNA from two orders of magnitude fewer lymphocytes than the other carriers. Thus poly I was found to be a superior carrier molecule for microscale RNA preparations suitable for reverse transcription and subsequent amplification using the polymerase chain reaction.