DCAF1, also known as VprBP (HIV-1-viral-protein-r-binding-protein), is an evolutionary conserved substrate-binding subunit of CRL4 (Cul4a-Ddb1-Roc1) ubiquitin ligase complex. It is a cellular protein targeted by HIV-1 viral protein R (Vpr). DCAF1 modulates cellular response against HIV in macrophages, controls the survival and reprogramming of oocyte, and regulates G2/M transition. DCAF1 functions through diverse mechanisms including regulating protein poly-ubiquitination, mono-ubiquitination and phosphorylation. Nonetheless, whether and how DCAF1 controls the function of primary T cell, a major cell type infected by HIV, remains unknown. We found DCAF1 is required for cell size growth and cell cycle entry from quiescence. To investigate the underlying molecular mechanisms and identify the cellular factors that associate with DCAF1 in T cells, we analyzed DCAF1-interacting proteins in T cells using VprBP immunoprecipitation and mass spectrometry.