Hrr25/CK1δ-directed release of Ltv1 from pre-40S ribosomes is necessary for ribosome assembly and cell growth.
Bottom Line: Conversely, phosphomimetic Ltv1 variants rescued viability after Hrr25 depletion.Finally, Ltv1 knockdown in human breast cancer cells impaired apoptosis induced by CK1δ/ε inhibitors, establishing that the antiproliferative activity of these inhibitors is due, at least in part, to disruption of ribosome assembly.These findings validate the ribosome assembly pathway as a novel target for the development of anticancer therapeutics.
Affiliation: Department of Cancer Biology and Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458.Show MeSH
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Mentions: To test if reconstituted ribosomes accurately mimic native pre-40S ribosome intermediates purified from yeast, we used cryo-EM (Strunk et al., 2011). ΔLtv1 subunits were reconstituted with Enp1–Ltv1–Rps3 as above, before preparation of specimens for cryo-EM data acquisition (see Materials and methods). Comparison of the reconstituted pre-40S subunits with the ΔLtv1 subunits established additional density in the beak area where the Enp1–Ltv1–Rps3 complex is located (Figs. 2 and S1). Furthermore, a side view shows that the beak is retracted after the addition of Enp1–Ltv1–Rps3, as observed in the native purified pre-40S assembly intermediates (Strunk et al., 2011). Indeed, a comparison of the reconstituted pre-40S subunits with native pre-40S subunits shows that these structures are superimposable (Fig. 2). Thus, the in vitro delivery of Rps3 produces a molecule indistinguishable from native assembly intermediates, thereby validating the in vitro reconstitution.
Affiliation: Department of Cancer Biology and Department of Chemistry, The Scripps Research Institute, Jupiter, FL 33458.