Simultaneous mapping of RNA ends (SMORE-seq) provides a method for determining the 5′ ends of transcripts (38 (link)). This technique allows for precise mapping of transcription start sites, and, can also allow the detection of short antisense RNAs that are difficult to detect by standard RNA-seq methods. In particular, this technique can be used to identify antisense transcripts arising from between tandemly arranged genes, which we term UAN-RNAs (for sites of (promoter) upstream antisense non-coding RNA transcription). SMORE-seq was performed as previously described (38 (link)). Briefly, RNA was incubated with tobacco acid pyrophosphatase (TAP, Epicentre) to remove 5′ caps. TAP was inactivated by heating at 65°C and RNA was purified. A control reaction omitting TAP was also carried out. Purified RNAs were then used for construction of Illumina RNA-seq libraries using the NEBNext Small RNA kit following manufacturer's instructions and as previously described (38 (link)). For our analysis, we combined data from our previously published study (GSE49026) with newly generated datasets.