CapSeq maps potential transcription start sites . In this method, total RNA is treated with terminator 5′-phosphate-dependent exonuclease to degrade rRNAs, calf intestinal phosphatase (CIP) to remove 5′ phosphates, and tobacco acid pyrophosphatase (TAP) to remove 5′ caps. The resulting long-capped RNAs are ligated to a 5′ adaptor. The first-strand cDNA is primed using a pool of random octamers and sequenced after size selection. Sequencing helps determine potential transcription start sites for PolII loci.