Replication forks temporarily or terminally pause at hundreds of hard-to-replicate regions around the genome. A conserved pair of budding yeast replisome components Tof1-Csm3 (fission yeast Swi1-Swi3 and human TIMELESS -TIPIN) act as a "molecular brake" and promote fork slowdown at proteinaceous replication fork barriers (RFBs), while the accessory helicase Rrm3 assists the replisome in removing protein obstacles. Here we show that the Tof1-Csm3 complex promotes fork pausing independently of Rrm3 helicase by recruiting topoisomerase I (Top1) to the replisome. Topoisomerase II (Top2) partially compensates for the pausing decrease in cells when Top1 is lost from the replisome. The C terminus of Tof1 is specifically required for Top1 recruitment to the replisome and fork pausing but not for DNA replication checkpoint (DRC) activation. We propose that forks pause at proteinaceous RFBs through a "sTOP" mechanism ("slowing down with topoisomerases I-II"), which we show also contributes to protecting cells from topoisomerase-blocking agents.
17Replication forks temporarily or terminally pause at hundreds of hard-to-replicate regions around the 18 genome. A conserved pair of budding yeast replisome components Tof1-Csm3 (fission yeast Swi1-Swi3 and 19 human TIMELESS-TIPIN) acts as a 'molecular brake' and promotes fork slowdown at proteinaceous 20 replication fork barriers (RFBs), while the accessory helicase Rrm3 assists the replisome in removing protein 21 obstacles. Here we show that Tof1-Csm3 complex promotes fork pausing independently of Rrm3 helicase by 22 recruiting topoisomerase I (Top1) to the replisome. Topoisomerase II (Top2) partially compensates for the 23 pausing decrease in cells when Top1 is lost from the replisome. The C-terminus of Tof1 is specifically 24 required for Top1 recruitment to the replisome and fork pausing but not for DNA replication checkpoint 25 (DRC) activation. We propose that forks pause at proteinaceous RFBs through a 'sTOP' mechanism ('slowing 26 down with TOPoisomerases I-II'), which we show also contributes to protecting cells from topoisomerase-27 blocking agents. 28 29
The ovulatory homolog model of female orgasm posits that the neuro-endocrine mechanisms underlying female orgasm evolved from and are homologous to the mechanisms mediating copulation-induced ovulation in some mammals. This model predicts that pharmacological agents that affect human orgasm, such as fluoxetine, should also affect ovulation in animals with copulation-induced ovulation, such as rabbits. We tested this prediction by treating rabbits with daily doses of fluoxetine for 2 wk and found that fluoxetine treatment reduces the number of ovulations postcopulation by 30%. In a second experiment we tested whether this result was mediated by an effect on the brain or via peripheral serotonin functions. We treated animals with fluoxetine and induced ovulation with a single injection of human chorionic gonadotropin. In this experiment ovulation rate was nominally reduced by only 8%, which is statistically not significant. We conclude that the effect of fluoxetine on copulation-induced ovulation rate supports the ovulatory homolog model of female orgasm, suggesting that female orgasm has very deep evolutionary roots among the early eutherian mammals.
The common human single nucleotide polymorphism rs3820282 is associated with multiple phenotypes ranging from gestational length to likelihood of endometriosis and ovarian cancer and can thus serve as a paradigm for a highly pleiotropic genetic variant. Pleiotropy makes it challenging to assign specific causal roles to particular genetic variants. Deleterious mutations in multifunctional genes may cause either the co-occurrence of multiple disorders in the same individuals (i.e., syndromes), or be repeatedly associated with a variety of disorders in a population. Moreover, the adverse effects can occur in combination with advantages in other traits, maintaining high frequencies of deleterious alleles in the population. To reveal the causal role of this specific SNP, we investigated the molecular mechanisms affected by rs3820282 in mice. We have shown previously that rs3820282 introduces a high affinity estrogen receptor 1 binding site at the Wnt4 locus. Having introduced this nucleotide substitution into the homologous site of the mouse genome by CRISPR/Cas 9 we show that this change causes a specific upregulation of Wnt4 transcription in the endometrial stromal cells during the preovulatory estrogen peak in late proestrus. Transcriptomic analysis of the whole uterus reveals broad systemic effects on uterine gene expression, including downregulation of proliferation and induction of many progesterone-regulated pro-implantation genes. The effect on proliferation is limited to the luminal epithelium, whereas other effects involve the uterine stromal compartment. We suggest that in the uterus, these changes could contribute to increased permissiveness to embryo invasion. Yet in other estrogen-responsive tissues, the same changes potentially lead to decreased resistance to invasion by cancer cells and endometriotic foci. A single molecular effect of rs3820282 on Wnt4 expression may thus underlie the various associated phenotypic effects.
Lack of adult cells’ ability to produce sufficient amounts of elastin and assemble functional elastic fibers is an issue for creating skin substitutes that closely match native skin properties. The effects of female sex hormones, primarily estrogen, have been studied due to the known effects on elastin post-menopause, thus have primarily included older mostly female populations. In this study, we examined the effects of female sex hormones on the synthesis of elastin by female and male human dermal fibroblasts in engineered dermal substitutes. Differences between the sexes were observed with 17β-estradiol treatment alone stimulating elastin synthesis in female substitutes but not male. TGF-β levels were significantly higher in male dermal substitutes than female dermal substitutes and the levels did not change with 17β-estradiol treatment. The male dermal substitutes had a 1.5-fold increase in cAMP concentration in the presence of 17β-estradiol compared to no hormone controls, while cAMP concentrations remained constant in the female substitutes. When cAMP was added in addition to 17β-estradiol and progesterone in the culture medium, the sex differences were eliminated, and elastin synthesis was upregulated by 2-fold in both male and female dermal substitutes. These conditions alone did not result in functionally significant amounts of elastin or complete elastic fibers. The findings presented provide insights into differences between male and female cells in response to female sex steroid hormones and the involvement of the cAMP pathway in elastin synthesis. Further explorations into the signaling pathways may identify better targets to promote elastic fiber synthesis in skin substitutes.
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