Acts both as a substrate recognition component of E3 ubiquitin-protein ligase complexes and as an atypical serine/threonine-protein kinase, playing key roles in various processes such as cell cycle, telomerase regulation and histone modification. Probable substrate-specific adapter of a DCX (DDB1-CUL4-X-box) E3 ubiquitin-protein ligase complex, named CUL4A-RBX1-DDB1-DCAF1/VPRBP complex, which mediates ubiquitination and proteasome-dependent degradation of proteins such as NF2. Involved in the turnover of methylated proteins: recognizes and binds methylated proteins via its chromo domain, leading to ubiquitination of target proteins by the RBX1-DDB1-DCAF1/VPRBP complex. The CUL4A-RBX1-DDB1-DCAF1/VPRBP complex is also involved in B-cell development: DCAF1 is recruited by RAG1 to ubiquitinate proteins, leading to limit error-prone repair during V(D)J recombination. Also part of the EDVP complex, an E3 ligase complex that mediates ubiquitination of proteins such as TERT, leading to TERT degradation and telomerase inhibition. Also acts as an atypical serine/threonine-protein kinase that specifically mediates phosphorylation of 'Thr-120' of histone H2A (H2AT120ph) in a nucleosomal context, thereby repressing transcription. H2AT120ph is present in the regulatory region of many tumor suppresor genes, down-regulates their transcription and is present at high level in a number of tumors. Involved in JNK-mediated apoptosis during cell competition process via its interaction with LLGL1 and LLGL2. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Protein modification; protein ubiquitination. Component of the DCX (DDB1-CUL4-X-box) E3 ubiquitin-protein ligase complex, named CUL4A-RBX1-DDB1-DCAF1/VPRBP complex. Interacts with DDB1; the interaction is direct. Also forms a ternary complex with DDA1 and DDB1. Interacts with NF2 (via FERM domain). Component of the EDVP complex, a E3 ligase complex containing DYRK2, EDD/UBR5, DDB1 and DCAF1. Interacts with DYRK2; the interaction is direct. Interacts with RAG1; the interaction is direct. Interacts with LLGL1 and LLGL2. Interacts with histone H3. Interacts with ESR1 and LATS1; probably recruited by LATS1 to promote ESR1 ubiquitination and ubiquitin-mediated proteasomal degradation. Associated with chromatin in a DDB1-independent and cell cycle-dependent manner: recruited to chromatin as DNA is being replicated and is released from chromatin before mitosis. Ubiquitously expressed. The protein kinase-like region mediates the threonine-protein kinase activity. The DWD boxes are required for interaction with DDB1. The chromo domain with a restricted pocket directly recognizes monomethylated substrates. Early embryonic lethality. Conditional knockout in mouse embryonic fibroblasts results in severely defective progression through S phase and subsequent apoptosis (PubMed:18606781). Conditional knockout in B lineage-specific cells arrests B-cell development at the pro-B-to-pre-B cell transition: mice display modest reduction of D-J(H) rearrangement, while V(H)-DJ(H) and V(kappa)-J(kappa) rearrangements are severely impaired. D-J(H) coding joints show longer junctional nucleotide insertions and a higher mutation frequency in D and J segments than normal (PubMed:22157821). Belongs to the VPRBP/DCAF1 family. Extended N-terminus.