  We calculate the nuclear enhancement in the angular distribution of Drell-Yan
pairs produced in proton-nucleus reactions. Nuclear effects are encoded in
universal twist-4 parton correlation functions. We find that the Lam-Tung
relation for the angular coefficients of the lepton-pair distribution holds for
the double-hard, but not for the soft-hard contribution. We also predict that
nuclear enhancement effects at RHIC energies can be large.
