Fig 5.

Yeast Las1 copurifies with preribosomes that also contain two 5′-3′ exoRNases (Rat1-Rai1 and Xrn1), three RNA helicases (Dbp2, Dbp3, and Has1), and several preribosome components. Partners of Las1 were identified by affinity purification and mass spectrometry analysis. Yeast cells expressing a functional Las1-TAP fusion were grown exponentially to mid-log phase at 30°C. Total lysates were prepared in solid phase and subjected to affinity purifications (see Materials and Methods). As a control, we used a strain expressing the TAP tag alone (TAP-only). All interactions are listed in Table S1 in the supplemental material. Interactants were identified by LC-MS/MS. Interactions were carefully curated with those identified in the TAP-only control and with an unrelated bait (see Materials and Methods). (Left) Major Las1 interactants sorted and color coded by known or putative function. RPS and RPL, ribosomal proteins from the small and large subunits, respectively. (Right) Eluates from representative Las1-TAP and TAP-only purifications were analyzed by 4 to 12% NuPage Novex Bis-Tris (Invitrogen), and the gel was stained with Coomassie blue. Las1-TAP is marked with an asterisk.