Human sister chromatids at metaphase are primarily linked by centromeric cohesion, forming the iconic X shape. Premature loss of centromeric cohesion disrupts orderly mitotic progression. Shugoshin (Sgo1) binds to and protects cohesin at inner centromeres. The kinetochore kinase Bub1 phosphorylates histone H2A at T120 (H2A-pT120) and recruits Sgo1 to kinetochores, 0.5 μm from inner centromeres. Here, we show that Sgo1 is a direct reader of the H2A-pT120 mark. Bub1 also recruits RNA polymerase II (Pol II) to unattached kinetochores and promotes active transcription at mitotic kinetochores. Mitosis-specific inactivation of Pol II traps Sgo1 at kinetochores and weakens centromeric cohesion. Sgo1 interacts with Pol II in human cells and with RNA in vitro. We propose that Pol II-dependent transcription enables kinetochore-bound Sgo1 initially recruited by H2A-pT120 to reach cohesin embedded in centromeric chromatin. Our study implicates mitotic transcription in targeting regulatory factors to highly compacted mitotic chromatin.

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Cohesin folds chromosomes via DNA loop extrusion. Cohesin-mediated chromosome loops regulate transcription by shaping long-range enhancer-promoter interactions, among other mechanisms. Mutations of cohesin subunits and regulators cause human developmental diseases termed cohesinopathy. Vertebrate cohesin consists of SMC1, SMC3, RAD21, and either STAG1 or STAG2. To probe the physiological functions of cohesin, we created conditional knockout (cKO) mice with Stag2 deleted in the nervous system. Stag2 cKO mice exhibit growth retardation, neurological defects, and premature death, in part due to insufficient myelination of nerve fibers. Stag2 cKO oligodendrocytes exhibit delayed maturation and downregulation of myelination-related genes. Stag2 loss reduces promoter-anchored loops at downregulated genes in oligodendrocytes. Thus, STAG2-cohesin generates promoter-anchored loops at myelination-promoting genes to facilitate their transcription. Our study implicates defective myelination as a contributing factor to cohesinopathy and establishes oligodendrocytes as a relevant cell type to explore the mechanisms by which cohesin regulates transcription.

Gateway vectors have been extensively developed to facilitate gene cloning in numerous species; however, a universal system that is compatible for multiple organisms was lacking. As a multipurpose expression vector, pCS2+ backbone-based expression plasmids are widely used for high-level expression of messenger RNAs (mRNAs) or proteins in mammalian/avian culture cells or Xenopus/zebrafish embryos. To date, a suite of vectors with pCS2+ backbone applicable for Gateway cloning system were unavailable yet. Here, we generated a set of Gateway destination vectors, named as pGCS (plasmids of Gateway in pCS2+) vectors, which can be fused to a choice of frequently used amino- or carboxyl-terminal tags, including MYC, HA, FLAG, His, GST, as well as eGFP fluorescent epitope. The systematic generation of this set of pCS2+ backbone-based Gateway destination vectors allows for in vitro recombination of DNA with high speed, accuracy, and reliability compared with the traditional 'digestion-ligation' cloning approach. Thus, our system accelerates the production of functional proteins, which could be widely expressed in a large variety of vertebrate organisms without tediously transferring genes into different expression vectors. Moreover, we make this series of Gateway vectors available to the research community via the non-profit Addgene Plasmid Repository.