[Comparative analysis of heat shock promoters efficiency in two diptera species]

Heat shock proteins (Hsp) provide cellular and whole body adaptation of animals to various adverse environmental conditions. Hsp70 is apparently the major player underlying biological adaptation in all organisms studied so far. In all animals the regulatory regions of studied heat shock genes include several conservative promoter elements HSEs (heat shock elements) that are necessary for binding of heat shock transcription factor (HSF). The promoter regions of hsp70 genes are extremely conserved and, hence, it was generally accepted that they are universal and can operate in species belonging to different phyla. In the present work we performed the comparative analysis which revealed characteristic differences in the hsp 70 promoters of two Diptera species: Drosophila melanogaster and highly thermotolerance soldier fly Stratiomys singularior. We measured promoters activity in D. melanogaster cell culture exploring in vitro luciferase reporter assay. The analysis demonstrated significantly higher strength ofD. melanogaster promoters in spite of the fact that comparable numbers of HSEs are present in both species. These drastic differences in the promoter strength are probably due to absence of GAF-binding sites, which are necessary for efficient functioning of D. melanogaster hsp70 promoters. In contrast, comparison of hsp83 promoters isolated from these two species does not show significant differences. Our results demonstrate existence of different evolutionary trends in the regulation of the hsp70 expression even within the same order (Diptera).

Novel arrangement and comparative analysis of hsp90 family genes in three thermotolerant species of Stratiomyidae (Diptera)

The heat shock proteins belonging to the Hsp90 family (Hsp83 in Diptera) play a crucial role in the protection of cells due to their chaperoning functions. We sequenced hsp90 genes from three species of the family Stratiomyidae (Diptera) living in thermally different habitats and characterized by extraordinarily high thermotolerance. The sequence variation and structure of the hsp90 family genes were compared with previously described features of hsp70 copies isolated from the same species. Two functional hsp83 genes were found in the species studied, that are arranged in tandem orientation at least in one of them. This organization was not previously described. Stratiomyidae hsp83 genes share a high level of identity with hsp83 of Drosophila, and the deduced protein possesses five conserved amino acid sequence motifs characteristic of the Hsp90 family as well as the C-terminus MEEVD sequence characteristic of the cytosolic isoform. A comparison of the hsp83 promoters of two Stratiomyidae species from thermally contrasting habitats demonstrated that while both species contain canonical heat shock elements in the same position, only one of the species contains functional GAF-binding elements. Our data indicate that in the same species, hsp83 family genes show a higher evolution rate than the hsp70 family.

Chernobyl-related thyroid cancer in children of Belarus: a case-control study

The accident at the Chernobyl nuclear power plant on April 26, 1986, released approximately 2 EBq of 131I and other radioiodine isotopes that heavily contaminated southern Belarus. An increase in thyroid cancer reported in 1992 and attributed to the Chernobyl accident was challenged as possibly the result of intensive screening. We began a case-control study to test the hypothesis that the Chernobyl accident caused the increase in thyroid cancer. Records of childhood thyroid cancer in the national therapy centers in Minsk in 1992 yielded 107 individuals with confirmed pathology diagnoses and available for interview. Pathways to diagnosis were (1) routine endocrinological screening in 63, (2) presentation with enlarged or nodular thyroid in 25 and (3) an incidental finding in 19. Two sets of controls were chosen, one matched on pathway to diagnosis, the other representing the area of heavy fallout, both matched on age, sex and rural/urban residence in 1986. The 131I dose to the thyroid was estimated from ground deposition of 137Cs, ground deposition of 131I, a data bank of 1986 thyroid radiation measurements, questionnaires and interviews. Highly significant differences were observed between cases and controls (both sets) with respect to dose. The differences persisted within pathway to diagnosis, gender, age and year of diagnosis, and level of iodine in the soil, and were most marked in the southern portion of the Gomel region. The case-control comparisons indicate a strong relationship between thyroid cancer and estimated radiation dose from the Chernobyl accident.

Urinary iodine excretion in Belarus children

Casual urine samples were collected to determine iodine excretion of 1680 Belarus children during 1990-1994. The subjects, 8-16 years old, were from nine different regions of Belarus; 60% were from the Gomel oblast, which has been associated with relatively high levels of radioiodine fallout and increased incidence of thyroid cancer. Most of the median values indicate borderline/low iodine intake or mild iodine deficiency. Ranges were wide but 163 children excreted < 20 micrograms I/l urine and they should be considered severely deficient in iodine.