Compartment A/B

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A/B区室是在早期Hi-C研究中发现的，整个基因组可以分为倾向于优先与自身区室相互作用的A区室和B区室。A区室与活跃表达的开放染色质相关联，而B区室则与不活跃表达的封闭染色质相关。这些区室自我交互，可能有助于蛋白质和其他因素如长非编码RNA在核内的局部化。

A/B compartments were first discovered in early Hi-C studies.Researchers noticed that the whole genome could be split into two spatial compartments, labelled "A" and "B", where regions in compartment A tend to interact preferentially with A compartment-associated regions than B compartment-associated ones. （其中区室A倾向于优先与A区室相互作用）Similarly, regions in compartment B tend to associate with other B compartment-associated regions.

A/B compartment-associated regions are on the multi-Mb scale and correlate with either open and expression-active chromatin ("A" compartments) or closed and expression-inactive chromatin ("B" compartments).A compartments tend to be gene-rich, have high GC-content, contain histone markers（组蛋白标记） for active transcription（转录）, and usually displace the interior of the nucleus. As well, they are typically made up of self-interacting domains and contain early replication origins. B compartments, on the other hand, tend to be gene-poor, compact, contain histone markers for gene silencing, and lie on the nuclear periphery. They are consisted mostly of LADs and contain late replication origins.

The fact that compartments self-interact is consistent with the idea that the nucleus localizes proteins and other factors such as long non-coding RNA (lncRNA) in regions suited for their individual roles.[citation needed] An example of this is the presence of multiple transcription factories throughout the nuclear interior.These factories are associated with elevated levels of transcription due to the high concentration of transcription factors (such as transcription protein machinery, active genes, regulatory elements, and nascent RNA). Around 95% of active genes are transcribed within transcription factories. Each factory can transcribe multiple genes - these genes need not have similar product functions, nor do they need to lie on the same chromosome. Finally, the co-localization of genes within transcription factories is known to depend on cell type.

A/B often compartments vary between cell types.

form:https://en.wikipedia.org/wiki/Nuclear_organization#A/B_compartments