PRO-seq data from chromosome 4 of Drosophila S2 cells.
PROseq is a disjoint GRanges object with 47380 ranges and 1
  metadata column, "score", which contains coverage of PRO-seq read 3' ends.
PROseq_paired is a GRanges object containing 53179 ranges and 1
  metadata column, "score", which indicates the number of identically-mapped
  reads (i.e. they share the same 5' and 3' ends).
An object of class GRanges of length 53179.
GEO Accession GSM1032758, run SRR611828.
Hojoong Kwak, Nicholas J. Fuda, Leighton J. Core, John T. Lis (2013). Precise Maps of RNA Polymerase Reveal How Promoters Direct Initiation and Pausing. Science 339(6122): 950–953. https://doi.org/10.1126/science.1229386