Nucleic Acid Packaging in Viruses.

Viruses shield their genetic information by enclosing the viral nucleic acid inside a protein shell (capsid), in a process known as genome packaging. Viruses follow essentially two main strategies to package their genome: Either they co-assemble their genetic material together with the capsid protein or an empty shell (procapsid) is first assembled and then the genome is pumped inside the capsid by a molecular motor that uses the energy released by ATP hydrolysis. During packaging the viral nucleic acid is highly condensed through a meticulous arrangement in concentric layers inside the capsid.

RUVBL1-RUVBL2 AAA-ATPase: a versatile scaffold for multiple complexes and functions.

RUVBL1 and RUVBL2 are two highly conserved AAA+ ATPases that form a hetero-hexameric complex that participates in a wide range of unrelated cellular processes, including chromatin remodeling, Fanconi Anemia (FA), nonsense-mediated mRNA decay (NMD), and assembly and maturation of several large macromolecular complexes such as RNA polymerases, the box C/D small nucleolar ribonucleoprotein (snoRNP) and mTOR complexes. How the RUVBL1-RUVBL2 complex works in such a variety of processes, sometimes antagonistic, has been obscure for a long time. Recent cryo-electron microscopy (cryo-EM) studies have started to reveal how RUVBL1-RUVBL2 forms a scaffold for complex protein-protein interactions and how the structure and ATPase activity of RUVBL1-RUVBL2 can be affected and regulated by the interaction with clients.

Molecular basis of tRNA recognition by the Elongator complex.

The highly conserved Elongator complex modifies transfer RNAs (tRNAs) in their wobble base position, thereby regulating protein synthesis and ensuring proteome stability. The precise mechanisms of tRNA recognition and its modification reaction remain elusive. Here, we show cryo-electron microscopy structures of the catalytic subcomplex of Elongator and its tRNA-bound state at resolutions of 3.

Structural asymmetry in the eukaryotic Elongator complex.

Nucleoside modifications in tRNA anticodons regulate ribosome dynamics during translation elongation and, thereby, fine-tune global protein synthesis rates. The highly conserved eukaryotic Elongator complex conducts specific C5-substitutions in tRNA wobble base uridines. It harbors two copies of each of its six individual subunits, which are all equally important for its activity.

Architecture of the yeast Elongator complex.

The highly conserved eukaryotic Elongator complex performs specific chemical modifications on wobble base uridines of tRNAs, which are essential for proteome stability and homeostasis. The complex is formed by six individual subunits (Elp1-6) that are all equally important for its tRNA modification activity. However, its overall architecture and the detailed reaction mechanism remain elusive.