| 1381. |
- Östling, Jonas
(författare)
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Function and regulation of the Yeast Mig1 repressor
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glucose repression is a global regulatory response in the yeast Saccharomyces cerevisiae. Thus, in the presence of glucose, the preferred carbon source, expression of many genes encoding proteins required for metabolism of other carbon sources are turned off.An important mediator of glucose repression is the Mig1 repressor. It is a DNA binding transcription factor that has two zinc fingers of the C2H2 type. When glucose is available, Mig1 binds to the promotors of glucose repressed genes and is then thought to recruit a large co-repressor complex, consisting of the Cyc8/Ssn6 and Tup1 proteins. Mig1 is negatively regulated by the Snf1 protein kinase, a protein which is essential for the expression of all glucose repressed genes in yeast.In this work, domains within the Mig1 repressor were characterized that mediate its carbon source regulation and its function as a repressor. An extensive deletion analysis of Mig1 revealed that an effector domain of 24 amino acid residues in the extreme C-terminus of the protein is important for repression. The C-terminal effector domain is structurally and functionally conserved also in the Mig1 homologues from the distantly related yeasts Kluyveromyces lactis and K. marxianus. A combined deletion analysis and alanine scanning mutagenesis of the effector domain in K. marxianus revealed that three leucines and one isoleucine are particularly important for its function in vivo.The deletion analysis of the Mig1 from S. cerevisiae also revealed that two internal domains, R1 and R2, are important for the regulation of Mig1 by glucose. Thus, a deletion of either R1 or R2 converts Mig1 to a constitutive repressor. Further experiments were conducted with a Mig1-VP16 hybrid activator in which the C-terminal effector domain was replaced by the activating, domain from the viral protein VP16 The analysis revealed that this hybrid activator is negatively regulated by Snf1. We further found that Mig1-VP16 is phosphorylated in the absence of glucose, and that this phosphorylation is dependent on Snf1. Point mutations in Mig1 -VP16 identified three serines that are important both for Snf1 control of Mig1-VP16 activity and for phosphorylation in the absence of glucose. Two of the serines are located in the R1 domain within sequence motifs similar to a consensus in vitro target site for Snf1. The third serine, which does not resemble the Snf1 consensus target site, is located near the zinc fingers adjacent to a basic domain, the B-domain, which is essential both for the function of Mig1-VP16 as an activator and for the function of Mig1 as a repressor.
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| 1382. |
- Östlund, Ingrid, 1951-
(författare)
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Aspects of Gestational Diabetes : Screening System, Maternal and Fetal Complications
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The appropriateness of universal screening for gestational diabetes mellitus (GDM) has been strongly questioned, since it does not satisfy ethical principles for screening. The aims of these studies were to determine the prevalence of GDM, expressed in terms of impaired glucose tolerance (IGT) and diabetes mellitus (DM), to evaluate different screening models using traditional anamnestic risk factors and repeated random B-glucose, to determine whether GDM increases risks for maternal complications such as preeclampsia, and to determine whether IGT during pregnancy, if left untreated, is associated with increased maternal or neonatal morbidity. Of 4,918 pregnant non-diabetic women attending maternal health care, 73.5% agreed to have a 75 g oral glucose tolerance test (OGTT). GDM was diagnosed in 1.7%, IGT in 1.3% and DM in 0.4%. Traditional risk factor criteria were fulfilled by 15.8%. Prior GDM and a prior macrosomic infant showed the highest association with GDM. No selective or two-step universal screening model would have detected all cases of GDM. A constructed model comprising prior GDM, a prior LGA/macrosomic infant, or a cut-off random B-glucose level of 8 mmol/l as an indication for OGTT reduced the need for OGTT to 7.3% compared to the selective screening model with traditional risk factors. Such a universal two-step screening model had 100% sensitivity for DM, and 44.7% sensitivity for IGT. The Swedish Medical Birth Register was used to evaluate GDM as risk factor for preeclampsia. GDM occurred in 0.8% and preeclampsia in 2.9% of 430,852 singleton pregnancies. There is an independent and significant association between GDM and preeclampsia. Obesity is a major confounding factor, but cannot explain the total excess risk. In a prospective population-based case-control study 213 women with untreated IGT during pregnancy were identified. For each case, four controls were recruited from the same delivery department. The analyses confirmed that maternal and fetal morbidity were increased in the cases in terms of cesarean section rate, pre-term delivery, Erb’s palsy and admission to NICU. There was a marked, independent increase in the proportion of LGA infants (OR 7.3; 95% CI 4.1-12.7). To determine whether treatment has an effect when IGT is diagnosed during pregnancy, a randomized study is required.
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| 1383. |
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| 1384. |
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