Ptip Associated Protein 1 (PA1)

C16ORF53 (PA1) is a component of a Set1-like multiprotein histone methyltransferase complex .By affinity purification of PTIP (PAXIP1)-associated proteins in a HeLa cell line expressing mouse Ptip, followed by mass spectrometry, Cho et al. (2007) identified C16ORF53, which they designated PA1.The predicted 254-amino acid protein shares 87% sequence identity with the mouse ortholog. When ectopically expressed in HeLa cells, PA1 localized to the nucleus.The protein complex is a Set1-like histone methyltransferase complex that displays histone H3 lysine-4 (H3K4) methyltransferase activity. GST pull-down assays showed that PA1 interacts directly with PTIP but not with ASH2L, RBBP5, WDR5, or NCOA6. PA1 requires PTIP for interaction with the rest of the complex.