Knockout malaria vaccine? Ménard, R. Nature 13 January (2005) A News and Views article on the finding that a genetically manipulated malaria parasite which cannot go through the liver stage of its life cycle can protect the host from further infection.

RNA silencing complex assembly and function Sontheimer, E. Nature Reviews Molecular Cell Biology February (2005) A review of recent biochemical and structural studies that have shed light on the RISC assembly pathway and have identified a possible endonuclease that is thought to be responsible for cleaving the target mRNA.

Nature and nurture — lessons from chemical carcinogenesis Luch, A. Nature Reviews Cancer February (2005)

Control of DNA replication and its potential clinical exploitation Gonzalez, M. A., Tachibana, K. K., Laskey, R. A. & Coleman, N. Nature Reviews Cancer February (2005) The authors of this Innovations article propose that minichromosome maintenance proteins — MCMs — and their regulators, both of which are part of the mechanism that limits DNA replication to once per cell cycle, could be used for routine cancer detection and prognosis.

Promoters in the environment: transcriptional regulation in its natural context Cases, I. & de Lorenzo, V. Nature Reviews Microbiology February (2005) The authors of this review look at how environmental bacterial promoters make sense of a wide variety of signals to determine the optimum transcriptional activity for survival.

In search of the limits of evolution Kondrashov, F. A. Nature Genetics January (2005) A News and Views on an article in which the authors look at trade-offs at the molecular level and find that it is possible to endow an enzyme with new functions without compromising its ability to carry out its original function.

Histone variants meet their match Sarma, K. & Reinberg, D. Nature Reviews Molecular Cell Biology February (2005) Aspects of chromatin function can be attributed to specific histone variants. This review discusses recent studies showing that specific chaperones recruit and exchange specific histone variants.

Differentiation by dispersal Coltman, D. W. Nature 6 January (2005) A News and Views piece on an article in the same issue which finds that, contrary to what is usually believed, gene flow between populations — in this case, of great tits — does not have to have a homogenizing effect.

Epigenetic mechanisms in memory formation Levenson, J. M. & Sweatt, J. D. Nature Reviews Neuroscience February (2005) Neurobiologists are beginning to investigate the possible roles of epigenetic mechanisms in behaviour, physiology and neuropathology. The authors review data that implicate epigenetic mechanisms in synaptic plasticity and memory formation.