Oxidised bases, such as 8-oxo-guanine, occur in cellular DNA as a result of attack by oxygen free radicals. The cancer-protective effect of vegetables and fruit is attributed to the ability of antioxidants in them to scavenge free radicals, preventing DNA damage and subsequent mutation. Antioxidant supplements (e.g., β-carotene, vitamin C) increase the resistance of lymphocytes to oxidative damage, and a negative correlation is seen between antioxidant concentrations in tissues and oxidised bases in DNA. Large-scale intervention trials with β-carotene have, however, (...) led to increases in cancer. Recent measurements of the frequency of oxidised DNA bases indicate that earlier estimates were greatly exaggerated; there may be only a few thousand 8-oxo-guanines per cell. Convincing evidence for mutations resulting from oxidative damage, in tumours or cultured cells, is lacking. It seems that efficient antioxidant defences together with DNA repair maintain a steady-state level of damage representing minimal risk to cell or organism. BioEssays 21:238–246, 1999. © 1999 John Wiley & Sons, Inc. (shrink)

Members of the Y‐box (YB) family of transcription factors are expressed in a wide range of cell types and are implicated in the regulation of a rapidly increasing number of genes. Although the biological activities of YB proteins appear to be varied, distinct patterns, relating to the timing of their expression and the identity of their target genes, are beginning to emerge. A recent report by Ito et al.(1) focusses attention on cell proliferation and adds support to earlier suggestions(2, 3) (...) that a primary function of YB proteins is to help activate growth‐associated genes. (shrink)

Divergent evolution can explain how many proteins containing structurally similar domains, which perform a variety of related functions, have evolved from a relatively small number of modules or protein domains. However, it cannot explain how protein domains with similar, but distinguishable, functions and similar, but distinguishable, structures have evolved. Examples of this are the RNA‐binding proteins containing the RNA‐binding domain (RBD), and a newly established protein group, the cold‐shock domain (CSD) protein family. Both protein domains contain conserved RNP motifs on (...) similar single‐stranded nucleic acid‐binding surfaces. Apart from the RNP motifs, which have a similar function, the two families show little similarity in topology or amino acid sequence. This can be considered an interesting example of convergent evolution at the molecular level. Previously, a β‐sheet surface was found to interact with RNA in non‐homologous proteins from yeast, phage and man, revealing that this mode of RNA binding may be a widely recurring theme. (shrink)

Oxidised bases, such as 8-oxo-guanine, occur in cellular DNA as a result of attack by oxygen free radicals. The cancer-protective effect of vegetables and fruit is attributed to the ability of antioxidants in them to scavenge free radicals, preventing DNA damage and subsequent mutation. Antioxidant supplements (e.g., β-carotene, vitamin C) increase the resistance of lymphocytes to oxidative damage, and a negative correlation is seen between antioxidant concentrations in tissues and oxidised bases in DNA. Large-scale intervention trials with β-carotene have, however, (...) led to increases in cancer. Recent measurements of the frequency of oxidised DNA bases indicate that earlier estimates were greatly exaggerated; there may be only a few thousand 8-oxo-guanines per cell. Convincing evidence for mutations resulting from oxidative damage, in tumours or cultured cells, is lacking. It seems that efficient antioxidant defences together with DNA repair maintain a steady-state level of damage representing minimal risk to cell or organism. BioEssays 21:238–246, 1999. © 1999 John Wiley & Sons, Inc. (shrink)