Trascription in Xenopus erythroid cells and their isolated nuclei
Trascription in Xenopus erythroid cells and their isolated nuclei
The transcriptional activity of Xeno us erythroid cells has been studied in vitro. Maturation is associated with a decrease in transcriptional activity brought about by a differential shut-down of gene activity. In the mature erythrocyte, the residual template activity is extremely low, apparently confined to the production of low molecular weight transcripts (45-113). If erythrocyte nuclei are isolated in an isotonic medium containing100 mM KC1, 5 mM MgCl, and 5 mM MnC12, the chromatin is maintained in its condensed form with the endogenous template activity barely detectable. Addition of E.coli RNA polymerase substantially increases the rate of transcription, but the pattern remains predominantly the same as that observed for whole cells. A large percentage of these transcripts are also found in nuclei that have not been exposed to bacterial polymerase. Preincubating erythrocyte nuclei in rat liver cytoplasm increases their transcriptional activity by up to 36-fold. Although the pattern of transcription appears essentially the same, approximately 250 of the sequences in cytoplasm-treated nuclei are not found in untreated nuclei, as judged by competitive hybridization. Up to 25% of these RNAs possess amino-acid accepting activity. Globin mRNA is not detectable in the nascent transcripts from normal or reactivated nuclei. This increase in transcription is not due to a RNase inhibitor, nor to RNA-dependent RNA synthesis. It is, however, detectable by homologous polymerases I and II, to differing extents, and can even be induced in erythroblast nuclei. A non-specific nicking enzyme Mass I) can mimic some of the properties of cytoplasmic reactivation, but not all. The possible role of nickases in transcriptional reactivation is discussed.
University of Southampton
1979
Gregory, Stephen Paul
(1979)
Trascription in Xenopus erythroid cells and their isolated nuclei.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The transcriptional activity of Xeno us erythroid cells has been studied in vitro. Maturation is associated with a decrease in transcriptional activity brought about by a differential shut-down of gene activity. In the mature erythrocyte, the residual template activity is extremely low, apparently confined to the production of low molecular weight transcripts (45-113). If erythrocyte nuclei are isolated in an isotonic medium containing100 mM KC1, 5 mM MgCl, and 5 mM MnC12, the chromatin is maintained in its condensed form with the endogenous template activity barely detectable. Addition of E.coli RNA polymerase substantially increases the rate of transcription, but the pattern remains predominantly the same as that observed for whole cells. A large percentage of these transcripts are also found in nuclei that have not been exposed to bacterial polymerase. Preincubating erythrocyte nuclei in rat liver cytoplasm increases their transcriptional activity by up to 36-fold. Although the pattern of transcription appears essentially the same, approximately 250 of the sequences in cytoplasm-treated nuclei are not found in untreated nuclei, as judged by competitive hybridization. Up to 25% of these RNAs possess amino-acid accepting activity. Globin mRNA is not detectable in the nascent transcripts from normal or reactivated nuclei. This increase in transcription is not due to a RNase inhibitor, nor to RNA-dependent RNA synthesis. It is, however, detectable by homologous polymerases I and II, to differing extents, and can even be induced in erythroblast nuclei. A non-specific nicking enzyme Mass I) can mimic some of the properties of cytoplasmic reactivation, but not all. The possible role of nickases in transcriptional reactivation is discussed.
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Published date: 1979
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Local EPrints ID: 462408
URI: http://eprints.soton.ac.uk/id/eprint/462408
PURE UUID: e2d79747-5164-46ef-9baf-6b08d73eea7e
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Date deposited: 04 Jul 2022 19:07
Last modified: 04 Jul 2022 19:07
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Author:
Stephen Paul Gregory
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