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.