| Molecular Function/Activity | Mechanism/Molecular Details | Binding Partners/Interactions | Key References |
|---|---|---|---|
| Histone binding | CHAF1B (CAF-1 p60) is a WD40-repeat subunit and the principal H3-H4-binding component of human CAF-1. Structural work showed one CAF-1 complex binds one H3-H4 heterodimer, with p60 contacting H4 through its ventral β-propeller surface and engaging a partially unfolded H3 region; this configuration helps prevent premature H3-H4 tetramerization. CHAF1B is required for CAF-1 histone binding and nucleosome assembly activity. | Histones H3.1/H4; CAF-1 subunits CHAF1A/p150 and RBBP4/p48 (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000008) | (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000008) |
| Nucleosome assembly | CHAF1B functions in replication-coupled chromatin assembly by helping CAF-1 deposit newly synthesized H3-H4 onto nascent DNA. CAF-1-H3-H4 complexes can dimerize on DNA, positioning two H3-H4 dimers for tetramer formation; structural data further suggest CAF-1 can promote a right-handed nucleosome precursor/di-tetrasome intermediate. | CAF-1 complex; nascent DNA; histone H3-H4 dimers; replication machinery (pqac-00000000, pqac-00000005, pqac-00000015, pqac-00000016) | (pqac-00000000, pqac-00000005, pqac-00000015, pqac-00000016) |
| DNA binding | Direct DNA-binding by CAF-1 is primarily assigned to CHAF1A domains, but structural and biochemical analyses indicate CHAF1B/p60 also contacts DNA in assembled intermediates and contains a DNA-binding surface adjacent to its H4-binding region. In the deposited complex, p60 appears to stabilize histone-DNA intermediates during chromatin assembly rather than acting as the main DNA-recruitment module. | DNA; histone-DNA assembly intermediates; CHAF1A KER/WHD domains cooperate at the complex level (pqac-00000015, pqac-00000016) | (pqac-00000015, pqac-00000016) |
| PCNA interaction | CAF-1 is targeted to replication forks through PCNA, enabling DNA synthesis-coupled chromatin assembly. The direct canonical PCNA-binding determinants map mainly to CHAF1A/p150, but CHAF1B acts within the PCNA-recruited CAF-1 complex at forks to execute H3-H4 deposition in S phase. | PCNA indirectly via CAF-1 complex architecture; replisome; nascent DNA (pqac-00000005, pqac-00000007, pqac-00000004) | (pqac-00000005, pqac-00000007, pqac-00000004) |
| ASF1 interaction | CHAF1B contains a C-terminal ASF1-interacting B domain that helps transfer newly synthesized H3-H4 from ASF1 to CAF-1. This positions CHAF1B as the handoff subunit linking upstream histone chaperoning to downstream nucleosome assembly. | ASF1; newly synthesized H3-H4; CAF-1 complex (pqac-00000000, pqac-00000004) | (pqac-00000000, pqac-00000004) |
| Heterochromatin formation | CAF-1, including CHAF1B, contributes to heterochromatin integrity and gene silencing by promoting nucleosome reassembly and supporting repressive chromatin states. Loss of CAF-1 function derepresses many genes, reduces proper silencing, and in viral systems diminishes repressive marks such as H3K9me3/H3K27me3 at latent genomes. | Repressive chromatin factors and marks including H3K9me3, H3K27me3, HP1-associated pathways; viral episomal chromatin (pqac-00000008, pqac-00000011, pqac-00000013) | (pqac-00000008, pqac-00000011, pqac-00000013) |
| Transcriptional regulation | CHAF1B influences transcription chiefly through chromatin assembly and accessibility control rather than sequence-specific DNA recognition. In hematopoietic and leukemia models, elevated CHAF1B helps maintain self-renewal and an undifferentiated state by repressing differentiation/tumor suppressor genes; depletion increases accessibility at selected loci and permits transcription factor binding. CHAF1B also restrains aberrant CENP-A chromatin incorporation, linking chromatin regulation to genome stability. | Chromatin at promoters/enhancers; lineage TFs such as ELF1 and C/EBPα (context-dependent at CAF-1-regulated loci); CENP-A/DAXX pathway in chromosomal stability assays (pqac-00000003, pqac-00000006, pqac-00000009, pqac-00000010, pqac-00000012) | (pqac-00000003, pqac-00000006, pqac-00000009, pqac-00000010, pqac-00000012) |


*Table: This table summarizes the core molecular activities attributed to human CHAF1B/CAF-1 p60, emphasizing what is direct versus complex-mediated. It is useful for distinguishing CHAF1B’s primary histone-chaperone role from broader CAF-1 functions in replication, heterochromatin, and transcriptional control.*