PAXIP1 and heart failure: In addition, a study performed on PAX-interacting protein 1 (PTIP)—an essential co-factor for methylation of histone H3 at Lys 4—showed that a loss of H3K4me3 in adult cardiomyocytes is sufficient to cause the down-regulation of Kv channel-interacting protein 2 (Kcnip2), which is repressed in heart failure and has a role in arrhythmogenesis.