Analysis of Local Chromatin States Reveals Gene Transcription Potential during Mouse Neural Progenitor Cell Differentiation.

Chromatin dynamics play a critical role in cell fate determination and maintenance by regulating the expression of genes essential for development and differentiation. In mouse embryonic stem cells (mESCs), maintenance of pluripotency coincides with a poised chromatin state containing active and repressive histone modifications. However, the structural features of poised chromatin are largely uncharacterized.

Histone variant H2A.Z regulates nucleosome unwrapping and CTCF binding in mouse ES cells.

Nucleosome is the basic structural unit of chromatin, and its dynamics plays critical roles in the regulation of genome functions. However, how the nucleosome structure is regulated by histone variants in vivo is still largely uncharacterized. Here, by employing Micrococcal nuclease (MNase) digestion of crosslinked chromatin followed by chromatin immunoprecipitation (ChIP) and paired-end sequencing (MNase-X-ChIP-seq), we mapped unwrapping states of nucleosomes containing histone variant H2A.

Structural transitions of centromeric chromatin regulate the cell cycle-dependent recruitment of CENP-N.

Specific recognition of centromere-specific histone variant CENP-A-containing chromatin by CENP-N is an essential process in the assembly of the kinetochore complex at centromeres prior to mammalian cell division. However, the mechanisms of CENP-N recruitment to centromeres/kinetochores remain unknown. Here, we show that a CENP-A-specific RG loop (Arg80/Gly81) plays an essential and dual regulatory role in this process.

E2F transcription factor 1 regulates cellular and organismal senescence by inhibiting Forkhead box O transcription factors.

E2F1 and FOXO3 are two transcription factors that have been shown to participate in cellular senescence. Previous report reveals that E2F1 enhanced cellular senescence in human fibroblast cells, while FOXO transcription factors play against senescence by regulation reactive oxygen species scavenging proteins. However, their functional interplay has been unclear.

Oncogene-induced telomere dysfunction enforces cellular senescence in human cancer precursor lesions.

In normal human somatic cells, telomere dysfunction causes cellular senescence, a stable proliferative arrest with tumour suppressing properties. Whether telomere dysfunction-induced senescence (TDIS) suppresses cancer growth in humans, however, is unknown. Here, we demonstrate that multiple and distinct human cancer precursor lesions, but not corresponding malignant cancers, are comprised of cells that display hallmarks of TDIS.

The ATTCT repeats of spinocerebellar ataxia type 10 display strong nucleosome assembly which is enhanced by repeat interruptions.

Nucleosome packaging influences many aspects of DNA metabolism such as replication, repair and transcription, and via this link likely has further downstream effects on genome stability. The instability and expansion of repetitive sequences is associated with at least 42 human diseases, yet the molecular conditions contributing to repeat instability have remained largely undetermined. Previously we showed strong nucleosome formation on CAG repeats associated with spinocerebellar ataxia type 1 and very weak formation on CGG repeats associated with fragile X syndrome, and that interruption of these repeat tracts made the DNA behave more like random sequences.

Friedreich's ataxia GAA.TTC duplex and GAA.GAA.TTC triplex structures exclude nucleosome assembly.

Both chromatin structure and formation of triplex DNA at expanded GAA TTC repeats have been shown to regulate the FXN gene silencing, which causes Friedreich's ataxia. Recent studies have suggested that the presence of heterochromatin at the long expanded GAA TTC repeats, which is enriched in hypoacetylated histones, deters the transcription of the FXN gene. However, neither direct histone binding nor the effect of histone acetylation on the GAA TTC duplex or the GAA GAA TTC triplex has been measured in vitro.