The sonication-resistant heterochromatin (srHC) fragments of mESCs were isolated by sucrose gradient ultracentrifugation, and the heterochromatin-associated proteins were enriched by Co-IP combined with mass spectrometry (Co-IP/MS) using anti-H3K9me3, IgG was used as a negative control. The Nat10 interacted proteins in mESCs were isolated by 3×Flag-Nat10 fusion protein overexpression and performed IP-MS using anti-Flag, IgG antibody was used as a negative control.