News & Views in 2005

Biochemical and genetic data defining the assembly pathway and structural biology of the T4 tail apparatus are merging to create a four-dimensional image reconstruction. Human inventions seem to be large-scale replicas of molecular devices honed by evolution.

Two recent studies address how chromatin-remodeling enzymes alter nucleosomes and suggest that they anchor on the particle while translocating on the nucleosomal DNA.

DNA helicases unwind DNA by a number of mechanisms in which conformational change seems to be of central importance. Characterization of two β-hairpins and fluorescence resonance energy transfer studies of protein-DNA interactions in the minichromosome maintenance proteins afford new insights into the molecular mechanisms of these proteins.

Two recent papers identify the first peptide inhibitor that binds to the structural protein of HIV-1, thereby blocking assembly of both immature and mature virus-like particles in vitro. These studies open the door to a strategy for the development of new therapies against the virus.

Two studies now explain why triplet DNA repeats tend to expand in the human genome, causing such severe hereditary neurological disorders as myotonic dystrophy and Huntington disease.

Two long-awaited structures of serine and tyrosine site-specific recombinases bound to DNA show how reactions that are basically the same can be carried out in surprisingly different ways.

The recent crystal structure of tetra nucleosomes supports zigzag-based models of chromatin fiber structure. The next challenge is to understand the modulation of chromatin structure in the nucleus, characterized by variability in DNA, histones and non-histone components.

The crystal structure of a four-protein complex comprising a SUMO ligase (E3), a SUMOylated protein substrate, and the cognate SUMO-conjugating enzyme sheds new light on catalysis, specificity and SUMO-protein interactions.

Four recent studies on the molecular architecture of amyloid fibrils made from different prion protein segments suggest commonalities among these fibrils. These studies also shed light on the structural distinctions between prion strains and the mechanism of fiber formation.

When and how the spliceosome assembles on its substrates in living yeast cells has been unclear. It is now evident that the 'when' is during transcription; the 'how' remains debatable.

MicroRNAs have established roles in negatively regulating messenger RNAs. Two plant microRNAs have recently been shown to target certain non-protein-coding RNAs for cleavage, adding a new dimension to the known roles of these tiny riboregulators.

Members of the sirtuin protein family link gene silencing and heterochromatin formation to NAD⁺-dependent histone deacetylation. Two papers now implicate O-acetyl-ADP-ribose, the metabolite produced by this reaction, as a small-molecule effector that binds to heterochromatic proteins.

The exosome is a complex composed of 3′→5′ exoribonucleases involved in RNA processing and degradation. The first high-resolution structure of the exosome core reveals a doughnut-like arrangement of six RNase PH–type subunits.

Translation termination, once thought to be the least complex of the steps in protein synthesis, is emerging as a process subject to considerable regulation. The prevalent mode for this regulation seems to be eRF-tweaking, the modulation of release factor activity by proteins involved in other gene expression pathways.

A recent study on the signaling conformation of the common receptor for the interleukin-6 family of cytokines, gp130, provides new insights into the activation mechanism of the 'tall' cytokine receptors.