Plays an important role in meiotic recombination. Stimulates DMC1-mediated strand exchange required for pairing homologous chromosomes during meiosis. The complex PSMC3IP/MND1 binds DNA, stimulates the recombinase activity of DMC1 as well as DMC1 D-loop formation from double-strand DNA. This complex stabilizes presynaptic RAD51 and DMC1 filaments formed on single strand DNA to capture double-strand DNA. This complex stimulates both synaptic and presynaptic critical steps in RAD51 and DMC1-promoted homologous pairing. May inhibit HIV-1 viral protein TAT activity and modulate the activity of proteasomes through association with PSMC3. Interacts with the DNA-binding domain of the nuclear receptors NR3C1/GR, ESR2/ER-beta, THRB and RXRA (By similarity). Forms a stable heterodimer with MND1. Interacts with PSMC3/TBP1. Highly expressed in testis and more specifically in spermatocytes. Detected in spleen, ovary and thymus. Overexpressed at day 11 in the embryo. Phosphorylated by PKA, PKC and MAPK. Infertility. Males exhibit testicular hypoplasia with lack of spermatozoa. Spermatocytes arrest at the stage of pachytene-like chromosome condensation and spermatogenesis is blocked at prophase of meiosis I. Axial elements are fully developed, but synapsis is limited. While meiotic double-stranded breaks are formed and processed, they fail to be repaired. Belongs to the HOP2 family.