Novel application of Phi29 DNA polymerase: RNA detection and analysis in vitro and in situ by target RNA-primed RCA.

We present a novel Phi29 DNA polymerase application in RCA-based target RNA detection and analysis. The 3'-->5' RNase activity of Phi29 DNA polymerase converts target RNA into a primer and the polymerase uses this newly generated primer for RCA initiation. Therefore, using target RNA-primed RCA, padlock probes may be targeted to inner RNA sequences and their peculiarities can be analyzed directly.

Duality of polynucleotide substrates for Phi29 DNA polymerase: 3'-->5' RNase activity of the enzyme.

Phi29 DNA polymerase is a small DNA-dependent DNA polymerase that belongs to eukaryotic B-type DNA polymerases. Despite the small size, the polymerase is a multifunctional proofreading-proficient enzyme. It catalyzes two synthetic reactions (polymerization and deoxynucleotidylation of Phi29 terminal protein) and possesses two degradative activities (pyrophosphorolytic and 3'-->5' DNA exonucleolytic activities).