RNA sequencing (RNA-seq) offers a snapshot of cellular RNA populations, but not temporal information about the sequenced RNA. Here Yale University researchers report TimeLapse-seq, which uses oxidative-nucleophilic-aromatic substitution to convert 4-thiouridine into cytidine analogs, yielding apparent U-to-C mutations that mark new transcripts upon sequencing. TimeLapse-seq is a single-molecule approach that is adaptable to many applications and reveals RNA dynamics and induced differential expression concealed in traditional RNA-seq.

 TimeLapse-seq uses a convertible nucleoside approach to identify
new transcripts in a sequencing experiment

(a) Scheme of TimeLapse-seq. (b) Restriction-enzyme-digestion assay probing the efficiency of U-to-C conversion.