This monoclonal was raised by injecting mice with yeast nuclear preparations and screening the resullting hybridomas by immunofluorescence on yeast cells. When this antibody was tested on cells from other species, including rat, mouse and human cells, it has invariably strongly stained nuclear pore complexes, so it appears to be an excellent and panspecific marker for these important structures. This antibody does not work well on western blots so we are currently unsure of the exact identity of the protein to which it binds.