Histone H4 acetylation and transcription in amphibian chromatin.

Abstract

Abstract. Lampbrush chromosomes from oocytes of the amphibian Triturus cristatus have been used to examine the role of histone acetylation in transcription by indirect immunofluorescence with antisera to H4 acetylated at specific lysine residues. Electrophoresis on acid-urea-Triton gels and Western blotting have confirmed the specificity of these antisera and defined the order in which particular lysine residues are acetylated in amphibian cells. As in mammals, lysine 16 is acetylated first, followed by 8 and/or 12 and then 5.With lampbrush chromosomes from immature (previtellogenic) oocytes, antisera to H4 acetylated at lysines 8, 12, and 16 labeled fluorescent foci at the bases of transcription loops. Antisera to H4 acetylated at lysine 5 labeled weakly (i.e., the tri-and tetraacetylated isoforms must be rare). Loops showed weak labeling of the chromatin axis but intense fluorescence at particular points, which probably represent incompletely decondensed chromatin. The RNP matrix of loops, including the RNP-rich sphere bodies and the dense matrix of "marker" loops, was not labeled. Treatment of immature oocytes with butyrate for 12 h to inhibit histone deacetylation did not affect immunolabeling, suggesting that turnover of H4 acetates is slow. In contrast, in chromosomes from mature oocytes, in which loops have retracted and transcription is low, butyrate caused an increase in labeling with all antisera, followed by the appearance of vestigial loops, weakly labeled, but with regions of intense fluorescence. These loops contain RNP and are presumably transcriptionally active. We conclude that H4 acetates turn over more rapidly in mature than immature oocytes and that histone hyperacetylation precedes, and possibly induces, loop formation and transcriptional activation.

Lampbrush chromosomes enable study of cohesin dynamics

“…The very high number of active elongation complexes on the axis of a loop does not prevent the association of histones, however. In good agreement with the intense transcriptional activity associated with these regions, histone H4 was found to be acetylated on different lysine residues (Sommerville et al 1993). Strikingly, newly expressed histones, such as H4, were shown by Dr. J.G.…”

DNA Topoisomerase II Is Not Detectable on Lampbrush Chromosomes but Enriched in the Amplified Nucleoli of Xenopus Oocytes

“…Although we cannot formally exclude this possibility, we consider it quite unlikely. Antibodies directed against chromatin constituents such as the core histones [27][28][29] and DNA [30] label the axis of the lampbrush chromosomes strongly, thus indicating that the specific chromomere organization does not exclude antibody binding. Furthermore, topo 11 is readily detectable on metaphase chromosomes of somatic cells despite their highly compact chromatin conformation.…”

Altered SMRT levels disrupt vitamin D3 receptor signalling in prostate cancer cells

“…In preliminary studies, we have examined the global histone acetylation status after cotreatment by extraction of total cellular histone from cells treated by single and combination treatments, and resolution on acid urea triton gels (Sommerville et al, 1993). The relatively low dose of TSA used (15 nM) readily increased global histone acetylation, that is, acetylation at all lysine residues examined (Histone H4 Lys shown) despite its ability to induce a comparable number of genes.…”