Transcription of DNA duplex containing deoxypseudouridine and deoxypseudoisocytidine, and inhibition of transcription by triplex forming oligonucleotide that recognizes the modified duplex.

We developed new DNA triplexes that contain four base triads T-A·T, A-ψ·CBr, G-PIC·YO, and C-G·Py+, where CBr, YO, Py, ψ, and PIC are 5-bromocytosine, 5-methyl-4-pyrimidone, 2-aminopyridine, the aglycons of deoxypseudouridine, and deoxypseudoisocytidine, respectively. DNA duplex incorporating T-A, A-ψ, G-PIC, and C-G, and triplex forming oligonucleotide incorporating T, CBr, YO, and Py formed the triplex as evaluated by Tm measurements. The triplex formation was successfully applied to the inhibition of transcription of the DNA duplex incorporating T7-promoter sequence modified by the above modified bases.