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

Fast-timing lifetime measurements of excited states in Cu-67

The half-lives of the 9/2(+), 13/2(+), and 15/2(+) yrast states in the neutron-rich Cu-67 nucleus were determined by using the in-beam fast-timing technique. The experimentally deduced E3 transition strength for the decay of the 9/2(+) level to the 3/2(-) ground state indicates that the wave function of this level might contain a collective component arising from the coupling of the odd proton p(3/2) with the 3(-) state in Ni-66. Theoretical interpretations of the 9/2(+) state are presented within the particle-vibration weak-coupling scheme involving the unpaired proton and the 3(-) state from Ni-66 and within shell-model calculations with a Ni-56 core using the jj44b residual interaction. The shell model also accounts reasonably well for the other measured electromagnetic transition probabilities