Classification of poly(A)- transcripts. (a) Classification of poly(A)- transcripts: EIs, excised introns; ZNF, zinc finger factor protein family. See text for details. (b) Overlapping analysis of the expression of poly(A)- transcripts in H9 and HeLa cells. (c) Example of a poly(A)- non-histone mRNA, znf460 and sesn3. The relative signals from either poly(A)+ or poly(A)- RNA preparations were normalized to those in the total RNA preparation in each cell line. Note that the signals from the poly(A)- samples are significantly enriched. Black arrows show the extended unannotated 3' UTR region of znf460. (d) An example of the excised 16th intron of the mRNA azi1. The blue box reveals the information in detail from this region. Note that the excised intron is abundant and can be detected only in the poly(A)- samples. (e) Examples of excised introns from different mRNAs, and the position of the excised intron in each mRNA is indicated.