The association of late-acting snoRNPs with human pre-ribosomal complexes requires the RNA helicase DDX21.

Translation fidelity and efficiency require multiple ribosomal (r)RNA modifications that are mostly mediated by small nucleolar (sno)RNPs during ribosome production. Overlapping basepairing of snoRNAs with pre-rRNAs often necessitates sequential and efficient association and dissociation of the snoRNPs, however, how such hierarchy is established has remained unknown so far. Here, we identify several late-acting snoRNAs that bind pre-40S particles in human cells and show that their association and function in pre-40S complexes is regulated by the RNA helicase DDX21.

Smac mimetic primes apoptosis-resistant acute myeloid leukaemia cells for cytarabine-induced cell death by triggering necroptosis.

The prognosis for patients with acute myeloid leukaemia (AML) is still poor, thus calling for novel treatment strategies. Here, we report that the small-molecule Smac mimetic BV6, which antagonizes Inhibitor of Apoptosis (IAP) proteins, acts in concert with cytarabine (AraC) to trigger cell death in AML cells in a highly synergistic manner (combination index 0.02-0.

Structural and functional analysis of the archaeal endonuclease Nob1.

Eukaryotic ribosome biogenesis requires the concerted action of numerous ribosome assembly factors, for most of which structural and functional information is currently lacking. Nob1, which can be identified in eukaryotes and archaea, is required for the final maturation of the small subunit ribosomal RNA in yeast by catalyzing cleavage at site D after export of the preribosomal subunit into the cytoplasm. Here, we show that this also holds true for Nob1 from the archaeon Pyrococcus horikoshii, which efficiently cleaves RNA-substrates containing the D-site of the preribosomal RNA in a manganese-dependent manner.

Backbone and side chain NMR resonance assignments for an archaeal homolog of the endonuclease Nob1 involved in ribosome biogenesis.

Eukaryotic ribosome biogenesis requires the concerted action of ~200 auxiliary protein factors on the nascent ribosome. For many of these factors structural and functional information is still lacking. The endonuclease Nob1 has been recently identified in yeast as the enzyme responsible for the final cytoplasmatic trimming step of the pre-18S rRNA during the biogenesis of the small ribosomal subunit.