Reviews & Analysis

According to the free-radical theory, oxidizing species — including hydrogen peroxide (H₂O₂) — are generated during aerobic respiration and cause molecular damage and ageing. However, recent evidence suggests that H₂O₂that is produced as a signalling molecule by a selected genetic programme regulates ageing.

Convergent mechanisms limit the amount of cellular damage and thereby protect against both cancer and ageing, whereas divergent mechanisms prevent excessive proliferation and, therefore, prevent cancer but promote ageing. The net balance between these mechanisms ensures a healthy, cancer-free lifespan until late adulthood in most individuals.

When quiescent cells re-enter the cell cycle, why do they require several extra hours in the G1 phase before they replicate their DNA? One hypothesis is that the proteins that are required for the formation of pre-replicative complexes are removed from chromatin.

In vitroembryonic stem (ES)-cell studies present a unique set of tools to understand embryonic development; however, these studies face many challenges. What are the current and future strategies for the exploitation of ES cells in developmental cell biology?

Transport of soluble proteins into the nucleus depends either on binding a protein-transport complex or on being small enough to diffuse in. Recent studies indicate that the delivery of integral membrane proteins into the inner nuclear membrane is governed by the same rules.

Recent studies have identified some of the factors that are involved in WNT secretion and have brought the focus of WNT research to the issue of how WNT proteins are secreted. What are the possible mechanisms that underlie this process?

Organelles adopt many complex and dynamic shapes that are often conserved throughout evolution. We are only beginning to understand the mechanisms by which organelle shape is generated and maintained and how, even in the same organelle, different morphologies are created.

Recent findings challenge the view that γ-tubulin-dependent formation of new microtubules is restricted to conventional microtubule-organizing centres and indicate that the spatio-temporal control of microtubule nucleation is more complex than was previously thought. So, how, where and when are microtubules made?

The chromatoid body, a unique cloud-like structure of male germ cells, has puzzled scientists for years. Recent findings indicate that microRNA and RNA-decay pathways converge at the chromatoid body, which might function as a germ-cell-specific RNA-processing centre.

It is surely time for water to take up its rightful position as the most important and active of all biological molecules. Liquid water is highly versatile — it can control, for example, the folding, structure, activity and interactions of macromolecules.

The SUN-domain family of nuclear envelope proteins interacts with KASH-domain proteins, which are also nuclear envelope proteins, to form 'bridges' across the inner and outer nuclear membranes. SUN-domain proteins are now proposed to provide a mechanical connection between the nucleoskeleton and the cytoskeleton.

What is the driving force behind periodic biological oscillations such as the circadian, hibernation and sleep–wake cycles? Temporal compartmentalization of metabolism has been shown in budding yeast, and might form the underlying basis for many of the rhythmic phenomena in biology.

Several non-coding RNAs that regulate eukaryotic mRNA transcription have recently been discovered. Their mechanisms of action and biological roles are extremely diverse, which indicates that, so far, we have only had a glimpse of this new class of regulatory factor.

What makes a stem cell is still poorly understood. Recent studies have uncovered that chromatin might hold some of the keys to how embryonic stem cells maintain their pluripotency, their ability to self-renew and induce lineage specification.

Lipid rafts, if they exist in resting cell membranes, are too small to be resolved by fluorescent microscopy and have no defined ultrastructure. However, recent studies with model membranes, computational modelling and innovative cell-biology techniques have provided new insights into plasma-membrane micro-organization.

Lipid droplets are the main lipid store in eukaryotic cells. Although the term lipid droplet is widely used, a unified nomenclature is lacking. So, could the terminology be consolidated? And what recent developments have there been in the field of lipid droplets?