Identification of a SCF-Saf1 ubiquitin ligase complex as an alternative recognition component for the eukaryotic fMet/N-degron pathway in Saccharomyces cerevisiae

Abstract

Eukaryotes synthesize Nt-formylated proteins, which act as a degradation signal (degron) for proteins. Nt-formylated proteins can help the cells overcome environmental challenges such as stationary phase, lack of specific amino acids, and cold stress. Psh1 recognizes specific Nt-formylated proteins such as Cse4, Rps22a and Pgd1. Therefore, to elucidate the degradation of Nt-formylated but probable substrates, other Nt-formylated proteins such as Smc6 and Lsm3 have been studied as model proteins. In the course of this research, a new fMet/N-recognin for the protein was identified: Saf1, an F-box protein in the SCF complex, can also degrade Nt-formylated proteins. Later, Saf1 was identified as a fMet/N-recognin. The E3 activity of Psh1 and Saf1 synergically regulates Nt-formylated Smc6 and Lsm3. This was a basic study to identify the regulatory conditions of fMet/N-recognins and to elucidate their action mechanisms in detail.