SUMOylation of TRIM28 is positively modulated by the BTB/POZ domain of Kaiso.

BACKGROUND

TRIM28 plays a crucial role in maintaining genomic stability and establishing imprinting, facilitated by the diversity of KRAB zinc finger proteins. The SUMOylation of TRIM28 is essential for its function and is enhanced in the presence of the KRAB domain. Previously, we demonstrated that Kaiso, another factor capable of interacting with TRIM28, can promote its SUMOylation. Here we investigate which structural elements of Kaiso are necessary for the hyper-SUMOylation of TRIM28.

METHODS AND RESULTS

We found that the SUMO-interacting motifs (SIMs) of Kaiso are not responsible for TRIM28 SUMOylation. The SUMOylation of individual TRIM28 domains in the presence of Kaiso was not observed, suggesting the importance of TRIM28's structural integrity for this process. The Kaiso BTB/POZ domain, but not its closest homolog ZBTB4, is sufficient for the effective hyper-SUMOylation of TRIM28. Also, using single-cell sequencing data of mouse embryos, we identified cells in which co-expression of Kaiso and TRIM28 occurs, including the immune system, nervous system and various epithelial cells.

CONCLUSIONS

BTB/POZ domain of Kaiso may function similarly to KRAB domains in its interaction with TRIM28 regulating its SUMOylation.