当前位置： SCI文献检索 > JOURNAL OF MOLECULAR BIOLOGY期刊下所有文献 > Reversible and irreversible changes in nucleosome structure along the c-fos and c-myc oncogenes following inhibition of transcription.

Reversible and irreversible changes in nucleosome structure along the c-fos and c-myc oncogenes following inhibition of transcription.

Abstract：

:A new affinity chromatographic procedure for the separation of transcriptionally active nucleosomes has been used to study the changes that take place in chromatin structure along the c-fos and c-myc genes when RNA synthesis is inhibited. Mercury-affinity chromatography separates the sulfhydryl-reactive nucleosomes of transcriptionally active genes from the compactly beaded, non-reactive nucleosomes of transcriptionally inert DNA sequences. The new procedure also discriminates between nucleosomes that have "unfolded" to reveal the previously shielded SH groups of histone H3 and nucleosomes that bind to the mercury column because of their association with thiol-containing non-histone proteins located in the transcription unit. Both classes of Hg-bound nucleosomes contain the c-fos and c-myc sequences, but only when they are being transcribed. We compared the effects of alpha-amanitin and actinomycin D on the transcription of c-fos and c-myc with the effects of each inhibitor on the distribution of the corresponding oncogenic DNA sequences in the chromatographically separated nucleosome fractions. It was found that the inhibition of RNA polymerase II by alpha-amanitin (added at the peaks of c-fos or c-myc expression in serum-stimulated BALB/c 3T3 cells) resulted in a rapid loss of affinity of the oncogene-containing nucleosomes for the mercury column. There was no corresponding effect on the mercury-binding properties of nucleosomes containing 28 S ribosomal gene sequences, which continue to be transcribed by amanitin-resistant RNA polymerase I. Therefore, the binding of the c-fos and c-myc nucleosomes to the mercury column seems to depend upon reversible structural changes associated with their transcription. Surprisingly, there was no corresponding loss of affinity of the c-fos and c-myc nucleosomes for the mercury column when actinomycin D was employed to inhibit RNA synthesis, despite the fact that transcription of both genes had been arrested abruptly. Measurements of [3H]actinomycin D binding show its preferential intercalation into the transcriptionally active nucleosomes. We suggest that the intercalation of actinomycin D into the DNA of active nucleosomes can lock the transcription complex into an "unfolded" but potentially active configuration. This was confirmed by run-off transcription assays showing a restoration of c-fos and c-myc RNA synthesis when actinomycin D was displaced by proflavine.

journal_name

J Mol Biol

journal_title

Journal of molecular biology

authors

Chen TA,Sterner R,Cozzolino A,Allfrey VG

doi

10.1016/0022-2836(90)90327-I

subject

Has Abstract

pub_date

1990-04-05 00:00:00

pages

481-93

issue

eissn

0022-2836

issn

1089-8638

pii

0022-2836(90)90327-I

journal_volume

212

pub_type

杂志文章

在线工具

Reversible and irreversible changes in nucleosome structure along the c-fos and c-myc oncogenes following inhibition of transcription.