Fig. 1.

28S rRNA fragments with homo- or heteropolymeric poly(A) tails in the cytoplasm and nuclei of human cells. (A) Fractionation purity was determined by Immunoblots (IBs) and RNA blots using fraction-specific markers: C, cytoplasm: GAPDH. N, nucleus: histone H3 (H3), fibrillarin, and U2/U3/U5-snoRNAs. T, total cell RNA/proteins. (B) Oligo(dT) RT-PCR isolation of truncated, adenylated 28S rRNA molecules from cyt (above) and nuc (below) fractions. 28S rRNA is schematically presented with arrows indicating primer locations and vertical lines showing tail sites and content (Table S1). (C) cRT-PCR isolation of truncated 28S rRNA molecules from cyt (above) and nuc (below) fractions. Cases in which it is not known whether the “A” is encoded or added posttranscriptionally are marked with an asterisk (Table S2).