Fig 1. Work-flow for the purification.

RNA and proteins were UV-cross linked at 254nm followed by 5 min of incubation with cycloheximide (CHX). Cells were lysed with detergent and the cleared lysate loaded onto a sucrose gradient (15–50% sucrose). The fractions containing actively translating polyribosomes were pooled and incubated with streptavidin sepharose beads for 1 h. The success of the purification was assessed by Northern blot. Proteins present in the purified mRNPs were detected by mass spectrometry (MS) or Western blot. SBP: streptavidin binding protein; RBPs: RNA binding proteins; UTR: untranslated region; ORF, open reading frame; CHX, cycloheximide; MS, mass spectrometry.