Proteins encoded by the human CYP3A genes metabolize every second drug currently in use. The activity of CYP3A gene products in the general population is highly variable and may affect the efficacy and safety of drugs metabolized by these enzymes. The mechanisms underlying this variability are poorly understood, but they include gene induction, protein inhibition and unknown genetic polymorphisms. To better understand the regulation of CYP3A expression and to provide a basis for a screen of genetic polymorphisms, we determined and analysed the sequence of the human CYP3A locus. The 231 kb locus sequence contains the three CYP3A genes described previously (CYP3A4, CYP3A5 and CYP3A7), three pseudogenes as well as a novel CYP3A gene termed CYP3A43. The gene encodes a putative protein with between 71.5% and 75.8% identity to the other CYP3A proteins. The highest expression level of CYP3A43 mRNA is observed in the prostate, an organ with extensive steroid metabolism. CYP3A43 is also expressed in several other tissues including liver, where it can be induced by rifampicin. CYP3A43 transcripts undergo extensive splicing. The identification of a new member of the CYP3A family and the characterization of the full CYP3A locus will aid efforts to identify the genetic variants underlying its variable expression. This, in turn, will lead to a better optimization of therapies involving the numerous substrates of CYP3A proteins.

Desulfotalea psychrophila is a marine sulfate-reducing delta-proteobacterium that is able to grow at in situ temperatures below 0 degrees C. As abundant members of the microbial community in permanently cold marine sediments, D. psychrophila-like bacteria contribute to the global cycles of carbon and sulfur. Here, we describe the genome sequence of D. psychrophila strain LSv54, which consists of a 3 523 383 bp circular chromosome with 3118 predicted genes and two plasmids of 121 586 bp and 14 663 bp. Analysis of the genome gave insight into the metabolic properties of the organism, e.g. the presence of TRAP-T systems as a major route for the uptake of C(4)-dicarboxylates, the unexpected presence of genes from the TCA cycle, a TAT secretion system, the lack of a beta-oxidation complex and typical Desulfovibrio cytochromes, such as c(553), c(3) and ncc. D. psychrophila encodes more than 30 two-component regulatory systems, including a new Ntr subcluster of hybrid kinases, nine putative cold shock proteins and nine potentially cold shock-inducible proteins. A comparison of D. psychrophila's genome features with those of the only other published genome from a sulfate reducer, the hyperthermophilic archaeon Archaeoglobus fulgidus, revealed many striking differences, but only a few shared features.

Synthesis and degradation of hsp70 mRNA was examined and compared in Hydra species living in different habitats and showing different heat-shock response. Hydra oligactis is restricted to habitats of low temperature and relatively stable pH. We have shown previously that this species is unable to acquire thermotolerance [Bosch, T., Krylow, S., Bode, H. & Steele, R. (1988) Proc. Natl Acad. Sci. USA 85, 7927Ϫ7931] and synthesizes significantly less heat-shock protein and hsp70 mRNA [Gellner, K., Praetzel, G. & Bosch, T. C. G. (1992) Eur. J. Biochem. 210, 683Ϫ691] in response to stress than related species, such as Hydra vulgaris or Hydra magnipapillata, which are adapted to habitats of wide temperature range and variable water quality. To examine the mechanisms responsible for the differential heatshock responses in these species, a construct containing H. magnipapillata hsp70 regulatory sequences fused to firefly luciferase was introduced into H. oligactis and H. magnipapillata polyps, and expression of luciferase examined. The results showed that luciferase can be expressed equally well in a heatinducible manner in both species, suggesting that H. oligactis heat-shock factor can interact with H. magnipapillata heat-shock elements. Northern blots of A-amanitin-treated polyps demonstrated that the half-life of hsp70 mRNA in heat-shocked H. oligactis is drastically shorter than in H. magnipapillata. Thus, differences in hsp70 mRNA stability appear to be responsible for the habitat-correlated differences in the stress response in Hydra species.Keywords : heat shock; hydra; RNA stability.All cells respond to stress with the synthesis of a small group of highly conserved proteins, termed heat-shock proteins [1,2]. One of the most conserved and best characterized heat-shock proteins is the 70-kDa heat-shock protein (Hsp70). The level of Hsp70 synthesis is controlled transcriptionally and posttranscriptionally through repression of hsp70 mRNA synthesis and destabilization of hsp70 transcripts [3]. The role of heat-shock proteins in protein folding, translocation through membranes and acquisition of thermotolerance has been the subject of numerous studies [4]. Research on heat-shock proteins, however, has been largely confined to cultured cells in the laboratory. Very little is known about the ecological significance of such proteins for organisms of closely related species living under different environmental conditions [5,6].When studying the stress response in the freshwater polyp Hydra, we observed differences in different species [7Ϫ9]. In response to stress Hydra vulgaris (formerly called Hydra attenuata [10]) and Hydra magnipapillata induce synthesis of several heat-shock proteins. In contrast, Hydra oligactis is unable to induce synthesis of heat-shock proteins and to acquire thermotolerance. The difference in the stress response is correlated with differences in the natural habitats : while H. vulgaris and H. magnipapillata polyps live in a wide range of freshwater environments under variable temperatures, H....

Hexaploid wheat is a young polyploid species and represents a good model to study mechanisms of gene evolution after polyploidization. Recent studies at the scale of the whole genome have suggested rapid genomic changes after polyploidization but so far the rearrangements that have occurred in terms of gene content and organization have not been analyzed at the microlevel in wheat. Here, we have isolated members of a receptor kinase (Lrk) gene family in hexaploid and diploid wheat, Aegilops tauschii, and barley (Hordeum vulgare). Phylogenetic analysis has allowed us to establish evolutionary relationships (orthology versus paralogy) between the different members of this gene family in wheat as well as with Lrk genes from barley. It also demonstrated that the sequences of the homoeologous Lrk genes evolved independently after polyploidization. In addition, we found evidence for gene loss during the evolution of wheat and barley. Analysis of large genomic fragments isolated from nonorthologous Lrk loci showed a high conservation of the gene content and gene organization at these loci on the homoeologous group 1 chromosomes of wheat and barley. Finally, sequence comparison of two paralogous fragments of chromosome 1B showed a large number of local events (sequence duplications, deletions, and insertions), which reveal rearrangements and mechanisms for genome enlargement at the microlevel.

A heat‐inducible, intron‐containing member of the hsp70 gene family has been isolated and characterized in Hydra magnipapillata and Hydra oligactis, two species previously shown [Bosch, T. C. G., Krylow, S. M., Bode, H. R. & Steele, R. E. (1988) Proc. Natl Acad. Sci. USA 85, 7927–7931] to differ in their stress response. The gene, hsp70.1, encodes a 654‐amino‐acid protein of predicted molecular mass 70 kDa with 78% amino acid identity to Xenopus HSP70. Northern‐blot analysis revealed that polyps of H. oligactis accumulate significantly less hsp70.1 mRNA after heat shock than polyps of H. magnipapillata. In nuclear run‐off experiments, we found that transcriptional induction of hsp70.1 expression in response to stress is similar in both species. Thus, the previously reported inability of H. oligactis to synthesize heat‐shock proteins in response to stress is at least in part due to reduced stability of hsp70.1 mRNA during heat shock.