A sumoylation wave to anchor the genome

Chromatin tethers to the nuclear envelope are lost during mitosis to facilitate chromosome segregation. How these connections are reestablished to ensure functional genome organization in interphase is unclear. Ptak et al. (2021. J. Cell Biol. https://doi.org/10.1083/jcb.202103036) identify a phosphorylation and SUMOylation-dependent cascade that links chromatin to the nuclear membrane during late mitosis

Angelika Amon (1967-2020):Breakthrough scientist, extraordinary mentor, and loyal friend

Visintin and Marston discuss the life and achievements of Angelika Amon, who passed away on October 29, 2020

Cdc55 coordinates spindle assembly and chromosome disjunction during meiosis

The PP2A regulatory subunit Cdc55 fine tunes the sequence and timing of both meiotic chromosome segregation events by limiting the activity of other phosphatases

Meiosis:DDK is not just for replication

SummaryHow is the chromosome segregation machinery modified to segregate homologs during meiosis I? The Dbf4-dependent Cdc7 kinase (DDK) has now been identified as a key regulator in this process

Shugoshins:Tension-sensitive pericentromeric adaptors safeguarding chromosome segregation

The shugoshin/Mei-S332 family are proteins that associate with the chromosomal region surrounding the centromere (the pericentromere) and that play multiple and distinct roles in ensuring the accuracy of chromosome segregation during both mitosis and meiosis. The underlying role of shugoshins appears to be to serve as pericentromeric adaptor proteins that recruit several different effectors to this region of the chromosome to regulate processes critical for chromosome segregation. Crucially, shugoshins undergo changes in their localization in response to the tension that is exerted on sister chromosomes by the forces of the spindle that will pull them apart. This has led to the idea that shugoshins provide a platform for activities required at the pericentromere only when sister chromosomes lack tension. Conversely, disassembly of the shugoshin pericentromeric platform may provide a signal that sister chromosomes are under tension. Here the functions and regulation of these important tension-sensitive pericentromeric proteins are discussed

Eco1-dependent cohesin acetylation anchors chromatin loops and cohesion to define functional meiotic chromosome domains

Cohesin organizes the genome by forming intra-chromosomal loops and inter-sister chromatid linkages. During gamete formation by meiosis, chromosomes are reshaped to support crossover recombination and two consecutive rounds of chromosome segregation. Here, we show that meiotic chromosomes are organized into functional domains by Eco1 acetyltransferase-dependent positioning of both chromatin loops and sister chromatid cohesion in budding yeast. Eco1 acetylates the Smc3 cohesin subunit in meiotic S phase to establish chromatin boundaries, independently of DNA replication. Boundary formation by Eco1 is critical for prophase exit and for the maintenance of cohesion until meiosis II, but is independent of the ability of Eco1 to antagonize the cohesin release factor, Wpl1. Conversely, prevention of cohesin release by Wpl1 is essential for centromeric cohesion, kinetochore mono-orientation, and co-segregation of sister chromatids in meiosis I. Our findings establish Eco1 as a key determinant of chromatin boundaries and cohesion positioning, revealing how local chromosome structuring directs genome transmission into gametes