Inter-chromosomal transcription hubs shape the 3D genome architecture of African trypanosomes.

The eukaryotic nucleus exhibits a highly organized 3D genome architecture, with RNA transcription and processing confined to specific nuclear structures. While intra-chromosomal interactions, such as promoter-enhancer dynamics, are well-studied, the role of inter-chromosomal interactions remains poorly understood. Investigating these interactions in mammalian cells is challenging due to large genome sizes and the need for deep sequencing.

Genome-Wide Profiling of Histone Modifications in Fission Yeast Using CUT&Tag.

Eukaryotic DNA is organized in the nucleus in the form of chromatin. Nucleosomes, the fundamental unit of chromatin, are subject to many posttranslational modifications (PTMs) as well as compositional variations through incorporation of histone variants. These alterations play important roles in regulation of genome structure and activity.

ChIPmentation for Epigenomic Analysis in Fission Yeast.

Histone modifications and transcription factor-DNA interactions regulate vital processes such as transcription, recombination, repair, and accurate chromosome segregation. Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) has been instrumental in studying genome-wide distribution of DNA-bound or chromatin-associated factors and histone posttranslational modifications (PTMs). Here, we describe a ChIPmentation protocol adapted for fission yeast, Schizosaccharomyces pombe.

A systematic analysis of chromatin factors identifies novel protein interaction networks associated with sites of transcription initiation and termination.

Nucleosomes composed of histones are the fundamental units around which DNA is wrapped to form chromatin. Transcriptionally active euchromatin or repressive heterochromatin is regulated in part by the addition or removal of histone post-translational modifications (PTMs) by "writer" and "eraser" enzymes, respectively. Nucleosomal PTMs are recognized by a variety of "reader" proteins that alter gene expression accordingly.

Large domains of heterochromatin direct the formation of short mitotic chromosome loops.

During mitosis chromosomes reorganise into highly compact, rod-shaped forms, thought to consist of consecutive chromatin loops around a central protein scaffold. Condensin complexes are involved in chromatin compaction, but the contribution of other chromatin proteins, DNA sequence and histone modifications is less understood. A large region of fission yeast DNA inserted into a mouse chromosome was previously observed to adopt a mitotic organisation distinct from that of surrounding mouse DNA.

Hap2-Ino80-facilitated transcription promotes de novo establishment of CENP-A chromatin.

Centromeres are maintained epigenetically by the presence of CENP-A, an evolutionarily conserved histone H3 variant, which directs kinetochore assembly and hence centromere function. To identify factors that promote assembly of CENP-A chromatin, we affinity-selected solubilized fission yeast CENP-A chromatin. All subunits of the Ino80 complex were enriched, including the auxiliary subunit Hap2.

Interspecies conservation of organisation and function between nonhomologous regional centromeres.

Despite the conserved essential function of centromeres, centromeric DNA itself is not conserved. The histone-H3 variant, CENP-A, is the epigenetic mark that specifies centromere identity. Paradoxically, CENP-A normally assembles on particular sequences at specific genomic locations.

Fitness Landscape of the Fission Yeast Genome.

The relationship between DNA sequence, biochemical function, and molecular evolution is relatively well-described for protein-coding regions of genomes, but far less clear in noncoding regions, particularly, in eukaryote genomes. In part, this is because we lack a complete description of the essential noncoding elements in a eukaryote genome. To contribute to this challenge, we used saturating transposon mutagenesis to interrogate the Schizosaccharomyces pombe genome.

Centromere DNA Destabilizes H3 Nucleosomes to Promote CENP-A Deposition during the Cell Cycle.

Active centromeres are defined by the presence of nucleosomes containing CENP-A, a histone H3 variant, which alone is sufficient to direct kinetochore assembly. Once assembled at a location, CENP-A chromatin and kinetochores are maintained at that location through a positive feedback loop where kinetochore proteins recruited by CENP-A promote deposition of new CENP-A following replication. Although CENP-A chromatin itself is a heritable entity, it is normally associated with specific sequences.

Shared regulatory sites are abundant in the human genome and shed light on genome evolution and disease pleiotropy.

Large-scale gene expression datasets are providing an increasing understanding of the location of cis-eQTLs in the human genome and their role in disease. However, little is currently known regarding the extent of regulatory site-sharing between genes. This is despite it having potentially wide-ranging implications, from the determination of the way in which genetic variants may shape multiple phenotypes to the understanding of the evolution of human gene order.

Epigenetics. Restricted epigenetic inheritance of H3K9 methylation.

Posttranslational histone modifications are believed to allow the epigenetic transmission of distinct chromatin states, independently of associated DNA sequences. Histone H3 lysine 9 (H3K9) methylation is essential for heterochromatin formation; however, a demonstration of its epigenetic heritability is lacking. Fission yeast has a single H3K9 methyltransferase, Clr4, that directs all H3K9 methylation and heterochromatin.

Long non-coding RNA-mediated transcriptional interference of a permease gene confers drug tolerance in fission yeast.

Most long non-coding RNAs (lncRNAs) encoded by eukaryotic genomes remain uncharacterized. Here we focus on a set of intergenic lncRNAs in fission yeast. Deleting one of these lncRNAs exhibited a clear phenotype: drug sensitivity.

Relaxed selection drives a noisy noncoding transcriptome in members of the Mycobacterium tuberculosis complex.

Related species are often used to understand the molecular underpinning of virulence through examination of a shared set of biological features attributable to a core genome of orthologous genes. An important but insufficiently studied issue, however, is the extent to which the regulatory architectures are similarly conserved. A small number of studies have compared the primary transcriptomes of different bacterial species, but few have compared closely related species with clearly divergent evolutionary histories.

Identification and characterization of the genetic changes responsible for the characteristic smooth-to-rough morphotype alterations of clinically persistent Mycobacterium abscessus.

Mycobacterium abscessus is an emerging pathogen that is increasingly recognized as a relevant cause of human lung infection in cystic fibrosis patients. This highly antibiotic-resistant mycobacterium is an exception within the rapidly growing mycobacteria, which are mainly saprophytic and non-pathogenic organisms. M.

A genome-wide screen in human embryonic stem cells reveals novel sites of allele-specific histone modification associated with known disease loci.

Background: Chromatin structure at a given site can differ between chromosome copies in a cell, and such imbalances in chromatin structure have been shown to be important in understanding the molecular mechanisms controlling several disease loci. Human genetic variation, DNA methylation, and disease have been intensely studied, uncovering many sites of allele-specific DNA methylation (ASM). However, little is known about the genome-wide occurrence of sites of allele-specific histone modification (ASHM) and their relationship to human disease.

Methicillin resistance alters the biofilm phenotype and attenuates virulence in Staphylococcus aureus device-associated infections.

Clinical isolates of Staphylococcus aureus can express biofilm phenotypes promoted by the major cell wall autolysin and the fibronectin-binding proteins or the icaADBC-encoded polysaccharide intercellular adhesin/poly-N-acetylglucosamine (PIA/PNAG). Biofilm production in methicillin-susceptible S. aureus (MSSA) strains is typically dependent on PIA/PNAG whereas methicillin-resistant isolates express an Atl/FnBP-mediated biofilm phenotype suggesting a relationship between susceptibility to β-lactam antibiotics and biofilm.

Sequencing and analysis of an Irish human genome.

Background: Recent studies generating complete human sequences from Asian, African and European subgroups have revealed population-specific variation and disease susceptibility loci. Here, choosing a DNA sample from a population of interest due to its relative geographical isolation and genetic impact on further populations, we extend the above studies through the generation of 11-fold coverage of the first Irish human genome sequence.

Results: Using sequence data from a branch of the European ancestral tree as yet unsequenced, we identify variants that may be specific to this population.

Modeling of surface-tension-driven flow of blood in capillary tubes.

Surface-tension-driven blood flow into a capillary tube, as in some medical devices, is studied. In a previous article, we considered the early stages of the entry flow from a drop of blood into a capillary, and solved the problem analytically under the assumption that the resistance of the air is negligible. In the present note we consider a capillary tube of finite length, with the far end containing a small window which opens to the atmosphere.

Bending stiffness of the lumbar spine subjected to posteroanterior manipulative force.

This study measured the bending stiffness of the spine when it is subjected to posteroanterior mobilization force. The lumbar spine was modeled as an initially curved beam column supported over the rib cage and the pelvis. Posteroanterior mobilization was assumed to be three-point bending of the beam.

Measurement of lumbar spine loads and motions during rotational mobilization.

Objectives: To measure the loads acting at the lumbar spine and the resulting motions during rotational mobilization.

Methods: Twenty healthy subjects were subjected to right rotational mobilization of different grades. The magnitude and frequency of mobilization loads were decided by an experienced manipulative therapist to be appropriate for each mobilization grade.