Histone H3.3 regulates mitotic progression in mouse embryonic fibroblasts

H3.3 is a histone variant that marks transcription start sites as well as telomeres and heterochromatic sites on the genome. The presence of H3.3 is thought to positively correlate with the transcriptional status of its target genes. Using a conditional genetic strategy against H3.3B, combined with short hairpin RNAs against H3.3A, we essentially depleted all H3.3 gene expression in mouse embryonic fibroblasts. Following nearly complete loss of H3.3 in the cells, our transcriptomic analyses show very little impact on global gene expression or on the localization of histone variant H2A.Z. Instead, fibroblasts displayed slower cell growth and an increase in cell death, coincident with large-scale chromosome misalignment in mitosis and large polylobed or micronuclei in interphase cells. Thus, we conclude that H3.3 may have an important under-explored additional role in chromosome segregation, nuclear structure, and the maintenance of genome integrity. © 2017 Published by NRC Research Press

Comparison of germinal center markers CD10, BCL6 and human germinal center-associated lymphoma (HGAL) in follicular lymphomas

<p>Abstract</p> <p>Background</p> <p>Recently, human germinal center-associated lymphoma (HGAL) gene protein has been proposed as an adjunctive follicular marker to CD10 and BCL6.</p> <p>Methods</p> <p>Our aim was to evaluate immunoreactivity for HGAL in 82 cases of follicular lymphomas (FLs) - 67 nodal, 5 cutaneous and 10 transformed - which were all analysed histologically, by immunohistochemistry and PCR.</p> <p>Results</p> <p>Immunostaining for HGAL was more frequently positive (97.6%) than that for BCL6 (92.7%) and CD10 (90.2%) in FLs; the cases negative for bcl6 and/or for CD10 were all positive for HGAL, whereas the two cases negative for HGAL were positive with BCL6; no difference in HGAL immunostaining was found among different malignant subtypes or grades.</p> <p>Conclusions</p> <p>Therefore, HGAL can be used in the immunostaining of FLs as the most sensitive germinal center (GC)-marker; when applied alone, it would half the immunostaining costs, reserving the use of the other two markers only to HGAL-negative cases.</p

Atomic Resolution Cryo-EM Structure Of A Nativelike CENP-A Nucleosome Aided By An Antibody Fragment

Genomic DNA in eukaryotes is organized into chromatin through association with core histones to form nucleosomes, each distinguished by their DNA sequences and histone variants. Here, we used a single-chain antibody fragment (scFv) derived from the anti-nucleosome antibody mAb PL2-6 to stabilize human CENP-A nucleosome containing a native α-satellite DNA and solved its structure by the cryo-electron microscopy (cryo-EM) to 2.6 Å resolution. In comparison, the corresponding cryo-EM structure of the free CENP-A nucleosome could only reach 3.4 Å resolution. We find that scFv binds to a conserved acidic patch on the histone H2A-H2B dimer without perturbing the nucleosome structure. Our results provide an atomic resolution cryo-EM structure of a nucleosome and insight into the structure and function of the CENP-A nucleosome. The scFv approach is applicable to the structural determination of other native-like nucleosomes with distinct DNA sequences

Long-term clonal persistence and evolution of t(14;18)-bearing B cells in healthy individuals

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t(11;14)-positive clones can persist over a long period of time in the peripheral blood of healthy individuals.

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Histone acetylation dynamics modulates chromatin conformation and allele-specific interactions at oncogenic loci.

In cancer cells, enhancer hijacking mediated by chromosomal alterations and/or increased deposition of acetylated histone H3 lysine 27 (H3K27ac) can support oncogene expression. However, how the chromatin conformation of enhancer-promoter interactions is affected by these events is unclear. In the present study, by comparing chromatin structure and H3K27ac levels in normal and lymphoma B cells, we show that enhancer-promoter-interacting regions assume different conformations according to the local abundance of H3K27ac. Genetic or pharmacological depletion of H3K27ac decreases the frequency and the spreading of these interactions, altering oncogene expression. Moreover, enhancer hijacking mediated by chromosomal translocations influences the epigenetic status of the regions flanking the breakpoint, prompting the formation of distinct intrachromosomal interactions in the two homologous chromosomes. These interactions are accompanied by allele-specific gene expression changes. Overall, our work indicates that H3K27ac dynamics modulates interaction frequency between regulatory regions and can lead to allele-specific chromatin configurations to sustain oncogene expression