(A) Effect of exosome subunit depletion on trypanosome growth. Cumulative growth curves are shown for depletion of the subunits shown. Below each curve is shown the effect of the depletion of RRP45, RRP4, or CSL4 on the abundances of RRP45, RRP44, and RRP4. The plus sign (+) indicates that normal levels of exosome are present. The vertical, downward-pointing arrow indicates that the level of the exosome subunit indicated above the growth curve is reduced. All panels are Western blots except that for CSL4, which is a Northern blot. CSM is an unrelated protein and SRP is the signal recognition particle RNA, both used as controls. RRP44 is an exonuclease that is not associated with the exosome. (B) The effects of RRP45 depletion on metabolic incorporation of 35S-labeled methionine. The upper panel shows autoradiography and the lower panel the corresponding Coommassie-stained gel. (C) The effects of RRP45, RRP4, or CSL4 depletion on 5.8 S rRNA maturation, analyzed as in Estévez et al. (2001).
