Plays an essential role in homologous recombination (HR) which is a major pathway for repairing DNA double-strand breaks (DSBs), single-stranded DNA (ssDNA) gaps, and stalled or collapsed replication forks. Acts as a molecular motor during the homology search and guides RAD51 ssDNA along a donor dsDNA thereby changing the homology search from the diffusion-based mechanism to a motor-guided mechanism. Plays also an essential role in RAD51-mediated synaptic complex formation which consists of three strands encased in a protein filament formed once homology is recognized. Once DNA strand exchange occured, dissociates RAD51 from nucleoprotein filaments formed on dsDNA (By similarity). Deficiency also resulted in an increased frequency of end-to-end chromosome fusions involving telomeres compared to the controls, suggesting a putative role in telomere capping. Non-homologous end joining (NHEJ) and homologous recombination (HR) represent the two major pathways of DNA double-strand break (DSB) repair in eukaryotic cells. LIG4 and RAD54L cooperate to support cellular proliferation, repair spontaneous DSBs, and prevent chromosome and single chromatid aberrations (PubMed:10209103, PubMed:10757799, PubMed:12218123, PubMed:12531026, PubMed:12548566, PubMed:12897131, PubMed:15175260, PubMed:9108475). ATP + H2O = ADP + H(+) + phosphate Homohexamer (By similarity). Interacts (via N-terminus) with RAD51 (By similarity). Interacts with NAP1L1 (By similarity). Interacts with BRD9; this interaction orchestrates RAD51-RAD54 complex formation (By similarity). Hardly detectable in most tissues. Dramatically increased in thymus, spleen and testis. Acetylated. Acetylation promotes interaction with BRD9, and subsequently with RAD54, which is essential for homologous recombination (HR). Phosphorylated. Phosphorylation at Ser-572 by NEK1 specifically in G2 phase allows efficient removal of RAD51 filaments from DNA. The nucleus of a mouse embryonic stem (ES) cell contains on average 2.4 x 10(5) molecules. Belongs to the SNF2/RAD54 helicase family.