Synthesis of 3'-O-fluorescently mono-modified reversible terminators and their uses in sequencing-by-synthesis.

Next-generation sequencing (NGS) technologies recently developed are now used for study of genomes from various organisms. Sequencing-by-synthesis (SBS) is a key strategy in the NGS. The SBS uses nucleotides so-called dual-modified reversible terminators (DRTs) in which bases are labeled with fluorophores and 3'-OH is protected with a reversibly cleavable chemical group, respectively. In this study, we examined the possibility of performing SBS with mono-modified reversible terminators (MRTs), in which the reversible blocking group on the 3'-OH plays a dual role as a fluorescent signal report as well as a chemical protection. We studied cyclic reversible termination by using two MRTs (dA and dT), wherein the modifications were two different fluorophores and cleavable to regenerate a free 3'-OH. We here demonstrated that SBS could be achieved with incorporation of MRTs by a DNA polymerase and correct base-calls based on the two different colors from the fluorophores.