RNA sequencing (RNA-seq) offers a snapshot of cellular RNA populations, but not temporal information about the sequenced RNA. Here we report TimeLapse-seq, a chemical method that uses oxidative-nucleophilic-aromatic-substitution to convert 4-thiouridine into cytidine analogues, 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.
