The Human Nucleolar Protein FTSJ3 Associates with NIP7 and Functions in Pre-rRNA Processing

NIP7 is one of the many trans-acting factors required for eukaryotic ribosome biogenesis, which interacts with nascent pre-ribosomal particles and dissociates as they complete maturation and are exported to the cytoplasm. By using conditional knockdown, we have shown previously that yeast Nip7p is required primarily for 60S subunit synthesis while human NIP7 is involved in the biogenesis of 40S subunit. This raised the possibility that human NIP7 interacts with a different set of proteins as compared to the yeast protein. By using the yeast two-hybrid system we identified FTSJ3, a putative ortholog of yeast Spb1p, as a human NIP7-interacting protein. A functional association between NIP7 and FTSJ3 is further supported by colocalization and coimmunoprecipitation analyses. Conditional knockdown revealed that depletion of FTSJ3 affects cell proliferation and causes pre-rRNA processing defects. The major pre-rRNA processing defect involves accumulation of the 34S pre-rRNA encompassing from site A′ to site 2b. Accumulation of this pre-rRNA indicates that processing of sites A0, 1 and 2 are slower in cells depleted of FTSJ3 and implicates FTSJ3 in the pathway leading to 18S rRNA maturation as observed previously for NIP7. The results presented in this work indicate a close functional interaction between NIP7 and FTSJ3 during pre-rRNA processing and show that FTSJ3 participates in ribosome synthesis in human cells

Probing particle-phonon-coupled states in the neutron-rich nucleus Cu-65 by lifetime measurements with fast-timing techniques

The Cu-65 nucleuswas populated by the Ni-64(Li-7,alpha 2n)Cu-65 reaction and the lifetime of the 9/2(+) state at 2.5 MeV was measured by electronic fast-timing technique, providing the value tau = 37(3) ps. The reduced transition probability B(E3) = 8.82(165) W.u. is deduced and compared to theoretical predictions in the framework of a particle-vibration (weak) coupling model. The results indicate that the 9/2(+) state is a member of the 3(-)circle times pi p3/2 multiplet, built by coupling the octupole 3(-) phonon of Ni-64 to an unpaired proton in the p(3/2) level, confirming the robustness of core excitations in the medium mass nucleus Ni-64

Mitochondrial complex III stabilizes complex I in the absence of NDUFS4 to provide partial activity.

Item does not contain fulltextMitochondrial complex I (CI) is a multi-subunit enzyme that forms the major entry point of nicotinamide adenine dinucleotide (NADH) electrons into the respiratory chain. Mutations in the NDUFS4 gene, encoding an accessory subunit of this complex, cause a Leigh-like phenotype in humans. To study the nature and penetrance of the CI defect in different tissues, we investigated the role of NDUFS4 in mice with fatal mitochondrial encephalomyopathy, caused by a systemic inactivation of the Ndufs4 gene. We report that the absence of NDUFS4 in different mouse tissues results in decreased activity and stability of CI. This CI instability leads to an increased disconnection of electron influx of the NADH dehydrogenase module from the holo-complex. However, the formation of respiratory supercomplexes still allows formation of active CI in these Ndufs4 knock-out mice. These results reveal the importance of these supramolecular interactions not only for stabilization but also for the assembly of CI, which becomes especially relevant in pathological conditions