Eukaryotic release factor 1 (eRF1) is a translation termination factor that binds
to the ribosome at stop codons. The expression of eRF1 is strictly controlled, since
its concentration defines termination efficiency and frequency of translational readthrough.
Here, we show that eRF1 expression inNeurospora crassais controlled by an autoregulatory
circuit that depends on the specific 3'UTR structure oferf1mRNA. The stop codon context
oferf1promotes readthrough that protects the mRNA from its 3'UTR-induced nonsense-mediated
mRNA decay (NMD). High eRF1 concentration leads to inefficient readthrough, thereby
allowing NMD-mediatederf1degradation. We propose that eRF1 expression is controlled
by similar autoregulatory circuits in many fungi and seed plants and discuss the evolution
of autoregulatory systems of different translation termination factors.
