Transcriptional activation of pericentromeric satellite repeats and disruption of centromeric clustering upon proteasome inhibition

Heterochromatinisation of pericentromeres, which in mice consist of arrays of major satellite repeats, are important for centromere formation and maintenance of genome stability. The dysregulation of this process has been linked to genomic stress and various cancers. Here we show in mice that the proteasome binds to major satellite repeats and proteasome inhibition by MG132 results in their transcriptional de-repression; this de-repression is independent of cell-cycle perturbation. The transcriptional activation of major satellite repeats upon proteasome inhibition is accompanied by delocalisation of heterochromatin protein 1 alpha (HP1α) from chromocentres, without detectable change in the levels of histone H3K9me3, H3K4me3, H3K36me3 and H3 acetylation on the major satellite repeats. Moreover, inhibition of the proteasome was found to increase the number of chromocentres per cell, reflecting destabilisation of the chromocentre structures. Our findings suggest that the proteasome plays a role in maintaining heterochromatin integrity of pericentromeres

Genetic variation in the CYP17 gene and recurrent spontaneous abortions

Purpose: The CYP17 gene encodes the enzyme cytochrome P450c17α, which functions at key steps in the synthesis process of human sex steroid hormones. A T/C polymorphism in the 5'\ gene has been described previously. Serum levels of androgens and estrogens have been shown to be elevated in individuals who carry the C substitution (Α2 allele). We hypothesized that variability in genes that control the sex hormone (estrogens, testosterone) biosynthesis might affect the pregnancy outcome. In the present study, we investigated the possible association between the T/C polymorphism of the promoter of CYP17 gene and the risk of recurrent spontaneous abortions in the Greek population. Methods: In the prospective case-control study, 148 patients and 134 healthy controls were studied. Women who had at least three unexplained spontaneous abortions before 20 weeks of gestation were included in the patient group. The PCR-RFLP method was used to genotype the subjects. Results: The frequencies of A1A1, A1A2, A2A2 genotypes were 0.34, 0.52, 0.14, respectively, in the patient group and 0.32, 0.47, 0.21, respectively, in the control group. The allele frequencies were 0.595 and 0.405 for A1 and A2, in the patient group and 0.555 and 0.445 for A1 and A2, respectively, in the control group. The data between the two groups were analyzed by χ2 test. Our results showed that there are no significant differences in genotype (P = 0.3883) or in allele frequencies (P = 0.3800) between the patient and the control group. Conclusion: The T/C promoter polymorphism of the CYP17 gene is not associated with the risk for recurrent spontaneous abortions in our Caucasian population. © 2010 Springer-Verlag