c("treatment: no treatment (mRNA)", "purification: oligo(dT)")
c("treatment: 4SU+6SG labeling and no UV", "purification: oligo(dT)")
c("treatment: 4SU+6SG labeling and biotin-purified", "purification: oligo(dT)")
c("treatment: 4SU+6SG labeling and UV", "purification: oligo(dT)")