Condensin II is anchored by TFIIIC and H3K4me3 in the mammalian genome and supports the expression of active dense gene clusters.

Structural maintenance of chromosome complexes, such as cohesin, have been implicated in a wide variety of chromatin-dependent functions such as genome organization, replication, and gene expression. How these complexes find their sites of association and affect local chromosomal processes is not well understood. We report that condensin II, a complex distinct from cohesin, physically interacts with TFIIIC, and they both colocalize at active gene promoters in the mouse and human genomes, facilitated by interaction between NCAPD3 and the epigenetic mark H3K4me3. Condensin II is important for maintaining high levels of expression of the histone gene clusters as well as the interaction between these clusters in the mouse genome. Our findings suggest that condensin II is anchored to the mammalian genome by a combination of H3K4me3 and the sequence-specific binding of TFIIIC, and that condensin supports the expression of active gene-dense regions found at the boundaries of topological domains. Together, our results support a working model in which condensin II contributes to topological domain boundary-associated gene activity in the mammalian genome.