RESUMEN
The phenomenon of association of transcribed genes into so-called transcription factories and also the role of these associations in spatial organization of the eukaryotic genome are actively discussed in the modern literature. Some authors think that the association of transcribed genes into transcription factories constitutes a major factor supporting the function-dependent three-dimensional organization of the interphase genome. In spite of the obvious interest in the problem of spatial organization of transcription in the eukaryotic cell nucleus, the number of experimental studies of transcriptional factories remains rather limited and the results of these studies are often contradictory. In the current review we have tried to critically re-evaluate the published experimental results that constitute the basis for current models and also the models themselves. We have especially analyzed the existing contradictions and attempted to explain them whenever possible. We also discuss new models that can explain the biological significance of clustering of transcribed genes and show possible mechanisms of the origin of transcription factories in the course of evolution.
Asunto(s)
Regulación de la Expresión Génica , Genoma , Familia de Multigenes , Transcripción Genética , Animales , Cromatina/genética , Cromatina/metabolismo , Orden Génico , Humanos , Modelos GenéticosRESUMEN
We have studied how the conditions in which the nuclear matrix is isolated influence the association of transcribing DNA with the nuclear matrix. Extraction of nuclease-treated nuclei with a low ionic strength solution before a high salt nuclei with a low ionic strength solution before a high salt extraction completely abolishes this association. However, RNA removal by RNAase treatment does not affect the binding of transcribing DNA to the nuclear matrix. The nature of the association of active genes with the nuclear matrix is discussed.
Asunto(s)
Núcleo Celular/ultraestructura , ADN/metabolismo , Transcripción Genética , Animales , Fraccionamiento Celular/métodos , Núcleo Celular/metabolismo , Células Cultivadas , Cobre/farmacología , Desoxirribonucleasas , Regulación de la Expresión Génica , Cadenas mu de Inmunoglobulina/genética , Cinética , Ratones , Concentración Osmolar , ARN/metabolismo , ARN Polimerasa II/metabolismo , Ribonucleasas , SolubilidadRESUMEN
Several preparations of nuclear matrices containing varying amounts of DNA were obtained from mouse plasmocytoma P3-X63-Ag8.653 cells and tested for the presence of RNA polymerase II activity. It has been demonstrated that about 25% of RNA polymerase II activity detected in the original nuclei can be recovered in isolated nuclear matrices. Only DNA-bound RNA polymerase II was found in the isolated matrices, while both free and DNA-bound RNA polymerase II activities were detected in the original nuclei. RNA polymerase II activity found in the isolated matrices did not depend on the portion of DNA recovered in the nuclear matrices in a large interval between 91 and 1.5% of DNA content in the original nuclei. The conclusion has been drawn that initiated RNA polymerase II molecules are non-randomly distributed along DNA loops. They are concentrated near the points of DNA attachment to the nuclear skeleton.
