Angiogenin, a potent angiogenic factor, was cloned and expressed by Escherichia coli and then purified with gel filtration chromatography. Approximately 90% pure angiogenin was obtained to generate a monoclonal antibody. Using western immunoblotting and ELISA, we confirmed that monoclonal antibody C46 secreted from hybridoma cells stably and specifically binds to angiogenin. The fused protein angiogenin-EGF was then expressed in HUVECs, and the subcellular localization of the recombinant protein was determined by confocal microscopy and TEM assay. Recombinant angiogenin was found to mainly concentrate in the pars granulosa of the nucleus, where the protein accumulates to form ribonucleoprotein particles.