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. Acts as a tissue specific coactivator of hormone-dependent transcription mediated by nuclear receptors. {ECO:0000269|PubMed:10806355, ECO:0000269|PubMed:16407260, ECO:0000269|PubMed:21963259}. This is the function of PSMC3IP (PSMC3 interacting protein, ENSG00000131470).