Nitric oxide and the post-transcriptional control of cellular iron traffic.

Nitric oxide (NO) is a small, labile and highly reactive molecule generated in various cells by NO synthases. Several important biological functions are controlled by this messenger, and recent data suggest a novel direct role for NO in post-transcriptional gene regulation mediated by iron regulatory protein (IRP). IRP is a cytoplasmic protein that coordinates cellular iron traffic by binding to iron-responsive elements in mRNAs encoding proteins involved in iron uptake, storage and utilization. NO activates the RNA-binding activity of this protein and in this regard mimics the consequences of iron starvation. Cell biological and biochemical data on the functions of NO and IRP suggest a mechanistic basis for these findings and raise the question of their biological implications.