The Complex of Proteins Associated with Set1 (COMPASS). The subunit arrangement model shown here is inspired from the cryo-electron microscopy (EM) structure published by Qu et al. in 2018 [74], which featured a truncated version of Set1, without the N-terminal. This region, as well as Shg1 and Swd2 subunits, have been added to the model (dotted lines). In red (Bre2, Sdc1, and Swd) are the subunits necessary for H3K4me2/3; in blue (Set1, Swd1, and Swd3) are the subunits necessary for H3K4me1/2/3; and in yellow is Spp1, which is necessary for H3K4me3. Little is known about Shg1. The structure is accompanied by several processes in which COMPASS subunits participate.