Capturing the Asc1p/eceptor for ctivated inase (RACK1) Microenvironment at the Head Region of the 40S Ribosome with Quantitative BioID in Yeast.

The Asc1 protein of is a scaffold protein at the head region of ribosomal 40S that links mRNA translation to cellular signaling. In this study, proteins that colocalize with Asc1p were identified with proximity-dependent tin entification (BioID), an labeling technique described here for the first time for yeast. Biotinylated Asc1p-birA*-proximal proteins were identified and quantitatively verified against controls applying SILAC and mass spectrometry.

Asc1p/RACK1 Connects Ribosomes to Eukaryotic Phosphosignaling.

WD40 repeat proteins fold into characteristic β-propeller structures and control signaling circuits during cellular adaptation processes within eukaryotes. The RACK1 protein of Saccharomyces cerevisiae, Asc1p, consists exclusively of a single seven-bladed β-propeller that operates from the ribosomal base at the head region of the 40S subunit. Here we show that the R38D K40E ribosomal binding-compromised variant (Asc1DEp) is severely destabilized through mutation of phosphosite T143 to a dephosphorylation-mimicking alanine, probably through proteasomal degradation, leading to asc1 phenotypes.