Histogram of distances between Transcription Start Site (TSS) and Coding Start (CDS). ATSS: based on 30,964 Alternative TSS from DBTSS database; RefSeq: based on 25,647 TSS from RefSeq database; DBTSS 5': based on 14,628 most upstream TSS from DBTSS database, a subset of ATSS. All data are binned by size of 1 kb, with registered on the x-axis by the middle point. Positive values in the x-axis indicate TSS is upstream of CDS. Note that there is no significant difference between RefSeq and DBTSS 5'. ATSS from DBTSS is present both up- and down-stream of CDS, with a symmetrical distribution around the bin of 500.