Immunolabelling of human metaphase chromosomes reveals the same banded distribution of histone H3 isoforms methylated at lysine 4 in primary lymphocytes and cultured cell lines

BACKGROUND: Using metaphase spreads from human lymphoblastoid cell lines, we previously showed how immunofluorescence microscopy could define the distribution of histone modifications across metaphase chromosomes. We showed that different histone modifications gave consistent and clearly defined immunofluorescent banding patterns. However, it was not clear to what extent these higher level distributions were influenced by long-term growth in culture, or by the specific functional associations of individual histone modifications. RESULTS: Metaphase chromosome spreads from human lymphocytes stimulated to grow in short-term culture, were immunostained with antibodies to histone H3 mono- or tri-methylated at lysine 4 (H3K4me1, H3K4me3). Chromosomes were identified on the basis of morphology and reverse DAPI (rDAPI) banding. Both antisera gave the same distinctive immunofluorescent staining pattern, with unstained heterochromatic regions and a banded distribution along the chromosome arms. Karyotypes were prepared, showing the reproducibility of banding between sister chromatids, homologue pairs and from one metaphase spread to another. At the light microscope level, we detect no difference between the banding patterns along chromosomes from primary lymphocytes and lymphoblastoid cell lines adapted to long-term growth in culture. CONCLUSIONS: The distribution of H3K4me3 is the same across metaphase chromosomes from human primary lymphocytes and LCL, showing that higher level distribution is not altered by immortalization or long-term culture. The two modifications H3K4me1 (enriched in gene enhancer regions) and H3K4me3 (enriched in gene promoter regions) show the same distributions across human metaphase chromosomes, showing that functional differences do not necessarily cause modifications to differ in their higher-level distributions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12863-015-0200-5) contains supplementary material, which is available to authorized users

Acetylation of core histones in response to HDAC inhibitors is diminished in mitotic HeLa cells

Histone acetylation is a key modification that regulates chromatin accessibility. Here we show that treatment with butyrate or other histone deacetylase (HDAC) inhibitors does not induce histone hyperacetylation in metaphase-arrested HeLa cells. When compared to similarly treated interphase cells, acetylation levels are significantly decreased in all four core histones and at all individual sites examined. However, the extent of the decrease varies, ranging from only slight reduction at H3K23 and H4K12 to no acetylation at H3K27 and barely detectable acetylation at H4K16. Our results show that the bulk effect is not due to increased or butyrate-insensitive HDAC activity, though these factors may play a role with some individual sites. We conclude that the lack of histone acetylation during mitosis is primarily due to changes in histone acetyltransferases (HATs) or changes in chromatin. The effects of protein phosphatase inhibitors on histone acetylation in cell lysates suggest that the reduced ability of histones to become acetylated in mitotic cells depends on protein phosphorylation