Chromatin assembly factor-1 (CAF-1) is a protein complex — including Chaf1a (p150), Chaf1b (p60), and p50 subunits — that assembles histone tetramers onto replicating DNA. CAF-1 functions as a histone chaperone that mediates the first step in nucleosome formation by tetramerizing and depositing newly synthesized histone H3/H4 onto DNA rapidly behind replication forks. Several studies have shown that the interaction between CAF-1 and PCNA, which stabilizes CAF-1 at replication forks, is important for CAF-1's role in nucleosome assembly