RNA biology of angiogenin: Current state and perspectives

Angiogenin (ANG) is a secreted ribonuclease best known for its ability to promote formation of blood vessels. Extensive research over many years has elucidated its structure and biophysical properties, although our knowledge of molecular mechanisms underlying ANG-associated biologic processes remains limited. Intriguingly, many of processes require the ribonuclease activity of ANG, thus highlighting the importance of identifying and characterizing RNA targets and intermediates of ANG-mediated endonucleolytic cleavage. While ANG demonstrates ribonuclease activity toward many RNA substrates in vitro, specific target of ANG, namely mature tRNA, was only recently identified in vivo. ANG-mediated tRNA cleavage is an unorthodox manner of generating non-coding RNAs with diverse biologic activities. In addition, the ribonuclease activity of ANG has been reported to be crucial for rRNA transcription. Here we critically discuss various aspects of ANG biology related to its RNase activity and discuss areas in need of further investigation.