S. Pandey et al., INHIBITION OF NUCLEAR-PROTEIN IMPORT BY A MONOCLONAL-ANTIBODY AGAINSTA NOVEL CLASS OF NUCLEAR-PORE PROTEINS, Experimental cell research, 212(2), 1994, pp. 243-254
Nuclear import of proteins is mediated by the nuclear pore complexes i
n the nuclear envelope and requires the presence of a nuclear localiza
tion signal (NLS) on the karyophilic protein. In this paper, we descri
be studies with a monoclonal antibody, Mab E2, which recognizes a clas
s of nuclear pore proteins of 60-76 kDa with a common phosphorylated e
pitope on rat nuclear envelopes. The Mab Ea-reactive proteins fraction
ated with the relatively insoluble pore complex-containing component o
f the envelope and gave a finely punctate pattern of nuclear staining
in immunofluorescence assays. The antibody did not bind to any cytosol
ic proteins. Mab E2 inhibited the interaction of a simian virus 40 lar
ge T antigen NLS peptide with a specific 60-kDa NLS-binding protein fr
om rat nuclear envelopes in photoaffinity labeling experiments. The an
tibody blocked the nuclear import of NLS-albumin conjugates in an in v
itro nuclear transport assay with digitonin-permeabilized cells, but d
id not affect passive diffusion of a small nonnuclear protein, lysozym
e, across the pore. Mab E2 may inhibit protein transport by directly i
nteracting with the 60-kDa NLS-binding protein, thereby blocking signa
l-mediated nuclear import across the nuclear pore complex. (C) 1994 Ac
ademic Press, Inc.