Nuclear RNA accumulations contain released transcripts and exhibit specific distributions with respect to Sm antigen foci.
RNA polymerase II transcripts accumulate within mammalian nuclei at distinct sites and exhibit varying morphology. Certain RNA species are organized in elongated structures, whereas others appear as dot-like concentrations. To analyze the status of the RNA within these accumulations, we investigated the composition of accumulations derived from Epstein-Barr virus (EBV) genes, human papilloma virus 18 (HPV18) open reading frames E6 and E7, as well as heat shock protein 89a (hsp89alpha) and 89beta (hsp89beta) genes. No differential distribution of exon and intron sequences within concentrations of EBV RNA could be observed. Whereas accumulations of hsp89alpha and hsp89beta always coincided with Sm antigen foci, the RNA of EBV and HPV18 never co-localized with these foci. This excludes Sm antigen foci as the only sites of splicing and suggests gene-specific variation in the nuclear localization of transcripts. Two sets of experiments were performed to assess whether transcripts in the RNA accumulations are in statu nascendi or products released from a discrete gene locus. Because RNA transcripts derived from EBV genes, which are located on both ends of the genome, were all distributed along the entire length of the RNA signals, they cannot be derived from a highly decondensed genomic DNA extending throughout elongated RNA accumulations. Furthermore, removal of labeled RNA sequences and subsequent visualization of DNA confirmed the confinement of the genomic sequences to a small subregion of the area occupied by accumulated RNA. Therefore, this study supports the view of RNA accumulations as a stream of molecules that delineate a path from a dot-like gene locus toward the nuclear envelope for export into the cytoplasm.
Lampel
S
S
Abteilung Organisation komplexer Genome, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Bridger
J M
JM
Zirbel
R M
RM
Mathieu
U R
UR
Lichter
P
P
D001324:Autoantigens / Q000032:analysis*; D002051:Burkitt Lymphoma; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000737:chemistry*; D003593:Cytoplasm / Q000737:chemistry; D004279:DNA, Viral / Q000032:analysis; D004268:DNA-Binding Proteins; D005091:Exons / Q000235:genetics; D005814:Genes, Viral / Q000235:genetics; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000235:genetics; D006801:Humans; D007438:Introns / Q000235:genetics; D009685:Nuclear Envelope / Q000737:chemistry; D009856:Oncogene Proteins, Viral / Q000235:genetics; D027383:Papillomaviridae / Q000235:genetics; D012322:RNA Precursors / Q000032:analysis; D012326:RNA Splicing; D012333:RNA, Messenger / Q000032:analysis*; D015138:RNA, Nuclear / Q000032:analysis*; D012367:RNA, Viral / Q000032:analysis; D017411:Ribonucleoproteins, Small Nuclear; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D055517:snRNP Core Proteins
D001324:Autoantigens; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; C052633:E7 protein, Human papillomavirus type 18; D006360:Heat-Shock Proteins; D009856:Oncogene Proteins, Viral; D012322:RNA Precursors; D012333:RNA, Messenger; D015138:RNA, Nuclear; D012367:RNA, Viral; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins