Amplification of human beta-actin gene by the reverse transcriptase-polymerase chain reaction: implications for assessment of RNA from formalin-fixed,paraffin-embedded material.

The polymerase chain reaction (PCR) is a powerful method that allows enzymatic amplification of rate target nucleic acid sequences. It has been applied to the amplification of viral genomes from paraffin-embedded pathology specimens. However, interpretation of negative results requires amplification of a housekeeping gene such as beta-actin. In the present study we used specific oligonucleotide primers previously designed to amplify both the genomic DNA and the mRNA transcript from paraffin-embedded tissue. These products have predicted sizes of 250 BP and 154 BP, respectively, but our results showed that PCR amplification only (without reverse transcription) unexpectedly generated the 154-BP product. Further investigation of the nature of this product demonstrated that it originated from the amplification of DNA, not RNA. We conclude that the 154-BP product generated by these primers cannot be exclusively considered as beta-actin RNA product and should not be used to assess successful extraction of RNA, to ascertain its integrity, or to normalize for the total amount of RNA assayed by RT-PCR from paraffin-embedded tissue.