Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 4 uppsatser.

Heme-activated proteins (HAPs) are transcription factors that have multiple roles in plant growth and development, such as embryogenesis, flowering time control, and drought tolerance. In the present study I found that HAP3b was also involved in controlling response to cold stress. Transcript profiling and gene expression analyses indicated that HAP3b repressed the CBF3 regulon under normal growth conditions. As a result, plants with HAP3b-overexpressed showed decreased survival rates while plants homozygous for the null allele hap3b showed an improved freezing tolerance compared to wild-type plants. To understand the mechanism of HAP3b in Arabidopsis, i.e. whether it also acts through forming a heterotrimer, the yeast two-hybrid system and the protein coimmunoprecipitation method were used to identify the proteins that could interact with HAP3b. From yeast two-hybrid analyses, it was found that HAP3b could interact with one (At3g14020) of ten HAP2s and all ten HAP5s tested. Further analyses showed that the newly identified HAP2 protein could only interact with two HAP5 proteins, those encoded by At5g63470 and At1g56170. To address whether HAPs also play important roles in major crop plants, HAP3 genes in barley (Hordeum vulgare L.) were identified and characterized. From database sequence analyses, cloning, and sequencing, it was found that barley plants have at least six full-length members in the HAP3 family. Phylogenetic analyses showed that each barley HAP3 was different, forming its own cluster with the HAP3s from other plant species. Each barley HAP3 also showed its own expression pattern in different tissues, at different developmental stages and under various environmental stresses. In particular, TC176294 showed the highest sequence similarity to HAP3b in Arabidopsis and its high expression was associated with flowering. In addition, TC176294 was upregulated by various abiotic stresses and by abscisic acid (ABA). Thus, TC176294 might be a barley ortholog of HAP3b. TC191694 showed the highest sequence similarity to HAP3c and might be a barley ortholog of HAP3c. TC191694 overexpression plants were early flowering compared to HAP3b-overexpression and wild-type plants while overexpression of TC176294 plants were not.

Thesis (M.S.)--University of Toledo, 2007 / "In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Sciences." Title from title page of PDF document. Bibliography: p. 37-48, 62-84.

Zona pellucida glycoproteins (ZP) are important proteins for maturation of the oocytes in eukaryotes, these proteins are encoded by cluster of zp genes. zp2.3 and zp3.5 genes are expressed during the developing and maturation of the oocytes in zebrafish ovaries. Both of the gens have a CCAAT box in their promoter regions, playing a big role in the expression of the both genes in zebrafish oocytes. The transcription of the genes in the eukaryotes requires transcription factors to initiate and promote the transcription, the transcription factors can bind to the promoter region and initiate the transcription process. The nuclear factor y (NFY) regulates the genes by binding to the CCAAT boxes in their promoter regions, it consist from many subunit such as NF-YA and NF-YB. Here in this study we characterize the expression pattern of NF-YA and NF-YB by screening these genes expression in several organs and tissues, also to determine its roles in the expression of the zp2.3 and zp3.5 genes in the adultzebrafish ovary.

No description available.

Le fer est un cofacteur essentiel à la croissance des organismes. Cependant, un surplus de fer conduit à la production de dérivés toxiques de l’oxygène qui sont dangereux pour les cellules. La concentration intracellulaire de fer doit donc être régulée. Lorsque la biodisponibilité du fer s’amenuise, la plupart des cellules augmentent leur acquisition du fer environnemental tout en réduisant sa consommation en réprimant plusieurs voies métaboliques fer-dépendantes non-essentielles. Alors que les mécanismes qui régissent l’augmentation de l’acquisition du fer sont assez bien caractérisés, les composantes qui contrôlent la promotion de l’économie du fer sont largement méconnues. Mes travaux ont porté sur l’étude des mécanismes de contrôle de l’économie du fer chez la levure à fission Schizosaccharomyces pombe. Php4, une sous-unité du complexe liant les boîtes CCAAT, est responsable de la répression des gènes codants pour des protéines qui utilisent du fer lorsque ce dernier est en faible concentration. Il est déjà connu qu’en présence de fer, l’expression du gène php4+ est réprimée via le facteur de transcription Fep1. De plus, la protéine Php4 est inactivée et exportée hors du noyau lorsque les cellules croissent en présence de fer. Ce processus est dépendant à la fois de la présence de l’exportine Crm1 et de la monothiol glutarédoxine Grx4. L’objectif de recherche est de découvrir le mécanisme par lequel Grx4 inhibe Php4 en réponse à la présence de fer. L’approche du double-hybride a été utilisée pour quantifier la force de l’interaction entre Php4 et Grx4 et identifier les domaines de ces protéines qui y participent. Ce système nous a permis de déterminer que Php4 interagit de façon constitutive avec le domaine thiorédoxine (TRX) de Grx4, alors que l’interaction entre Php4 et le domaine glutarédoxine (GRX) est dépendante de la présence de fer. Nous avons déterminé que la cystéine 35 du domaine TRX et la cystéine 172 du domaine GRX sont essentiels pour l’interaction de chacun de ces domaines avec Php4. Des régions minimales de Php4 nécessaires pour son interaction avec chacun des domaines GRX et TRX ont aussi été identifiées. Par la suite, nous avons démontré que l’expression du domaine GRX seul de Grx4 est suffisante pour l’inactivation de Php4 en présence de fer. Puis, par des essais de fluorescence par complémentation bimoléculaire (BiFC), nous avons démontré que le domaine GRX de Grx4 interagit de façon fer-dépendante avec Php4 et qu’il est suffisant pour l’exportation de Php4 hors du noyau en présence de fer. Ces résultats révèlent que le mécanisme par lequel Php4 est inhibé en présence de fer dépend de son interaction avec le domaine GRX de Grx4. À la suite des résultats obtenus, un modèle illustrant l’interaction fer-dépendante entre Grx4 et Php4 suggère la présence potentielle d’un centre fer-soufre qui pourrait expliquer la nature de l’interaction fer-dépendante entre les deux protéines.

Php4 is a subunit of the CCAAT-binding protein complex that has a negative regulatory function during iron deprivation in the fission yeast Schizosaccharomyces pombe. Under low iron conditions, Php4 fosters the repression of genes encoding iron using proteins. In contrast, under iron-replete conditions, Php4 is inactivated at both transcriptional and post-transcriptional levels. Our group has already described that Php4 is a nucleo-cytoplasmic shuttling protein, which accumulates into the nucleus during iron deficiency. On the contrary, Php4 is exported from the nucleus to the cytoplasm in response to iron abundance. Php4 possesses a leucine-rich NES (93LLEQLEML100) that is necessary for its nuclear export by the exportin Crm1. Our current study aims at understanding the mechanism by which Php4 is imported in the nucleus during iron starvation. Through microscopic analyses using different mutant strains, we showed that the nuclear localization of Php4 is independent of the other subunits of the CCAAT-binding core complex namely Php2, Php3 and Php5. Deletion mapping analysis of Php4 identifies two putative nuclear localization sequences (NLSs) in Php4 (171KRIR174 and 234KSVKRVR240). Using chimeric proteins that consist of GFP fused to Php4, we engineered substitutions of the basic amino acid residues 171AAIA174 and 234ASVAAAA240 and analyzed the functionality of both NLSs. We observed that both monopartite NLSs play critical role for Php4 nuclear localization. We also observed that mutant strains of cut15+, imp1+ or sal3+ exhibited defects in nuclear targeting of Php4, revealing that nuclear accumulation of Php4 is dependent on two karyopherin α (Imp1 and Cut15) and one karyopherin β (Sal3) receptors. Consistently, the Php4-mediated repression activity is abolished in the absence of two functional NLSs. Moreover, loss of Imp1, Cut15 or Sal3 resulted in increased expression of isa1+, which is a target gene of Php4. Co-immunoprecipitation assay (Co-IP) reveals physical interaction of Php4 with Imp1, Cut15 and Sal3 in vitro. Collectively, our results demonstrate that Php4 has two distinct NLS regions responsible for its nuclear localization. Furthermore, karyopherin α and β receptors play a role in the nuclear import of Php4. Because Php4 is essential for growth under low iron conditions, the presence of two NLSs would ensure the protein to reach its nuclear destination when cells undergo a transition from iron-sufficient to iron-limiting conditions.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--Case Western Reserve University, 2006. / [School of Medicine] Department of Pathology. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Thesis (Ph.D.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 161 pages. Includes Vita. Includes bibliographical references.