Transcribed DNA is preferentially located in the perichromatin region of mammalian cell nuclei.
The precise localization of transcribed DNA and resulting RNA is an important aspect of the functional architecture of the nucleus. To this end we have developed a novel in situ hybridization approach in combination with immunoelectron microscopy, using sense and anti-sense RNA probes that are derived from total cellular or cytoplasmic poly(A+) RNA. This new technology is much more gentle than classical in situ hybridization using DNA probes and shows excellent preservation of nuclear structure. Carried out on ultrathin sections of fixed and resin-embedded COS-7 cells, it revealed at high resolution the localization of the genes that code for the cellular mRNAs. Quantitative analysis shows that most transcribed DNA is concentrated in the perichromatin region, i.e. the interface between subchromosomal compact chromatin domains and the interchromatin space essentially devoid of DNA. The RNA that is produced is found mainly in the perichromatin region and the interchromatin space. These results imply that in the mammalian nucleus the chromatin fiber is folded so that active genes are predominantly present in the perichromatin region, which is the most prominent site of transcription.
Centre of Electron Microscopy, University of Lausanne, Bugnon 27, CH-1005 Lausanne, Switzerland.
Janusz
J
Niedojadlo
Cécile
C
Perret-Vivancos
Karl-Henning
KH
Kalland
Dusan
D
Cmarko
Thomas
T
Cremer
Roel
R
van Driel
Stanislav
S
Fakan
D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000737:chemistry*; D002522:Chlorocebus aethiops; D002843:Chromatin / Q000737:chemistry*; D004247:DNA / Q000032:analysis*; D017403:In Situ Hybridization / Q000379:methods; D012313:RNA / Q000096:biosynthesis; D015347:RNA Probes; D014158:Transcription, Genetic
D002843:Chromatin; D015347:RNA Probes; D012313:RNA; D004247:DNA