A SUMOylation wave to anchor the genome

Abstract

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.

Figure 1.

Re-establishment of chromatin tethering to the nuclear envelope in late mitosis. SUMO E3 ligase Siz2 is phosphorylated in mitosis, allowing its binding to VAP protein Scs2. The Scs2–Siz2 interaction involves the MSP motif on Scs2 and the FFAT motif on Siz2. Siz2 also SUMOylates Scs2, which stabilizes their interaction through SUMO–SIM binding. The resultant recruitment of Siz2 to the nuclear envelope leads to SUMOylation of multiple targets. This includes Sir4, SUMOylation of which promotes its association with telomeric chromatin. SUMOylation of an unknown target also leads to recruitment of the INO1 gene to nuclear pores.