The yeast two-hybrid system was used to isolate and characterize protein interactors of the N-terminal domain of the serine protease Omi/HtrA2 (high temperature requirement protein A2) encompassing amino acids 31-133. This large domain of Omi/HtrA2 is usually cleaved and removed through autoproteolysis to produce the mature form of the protein. Whether the N-terminal domain has any function after its removal is unknown. Omi/HtrA2 is involved in a variety of diseases including cancers, neurodegenerative disorders, and metabolic disorders, but thus far, it is assumed that its normal function is the degradation of specific substrates. To characterize any potential function of Omi/HtrA2’s unique amino terminus, specific interactors were isolated. One such interactor was the small GTPase Rab2A protein. We discuss the implications of this interaction and its biological significance.

While mitochondria are traditionally associated with energy production, recent studies identified its function in controlling the onset of apoptosis. Mitochondrial apoptotic control results from sequestering pro-apoptotic proteins, which are secreted following cellular stress. HtrA2/OMI is secreted from mitochondria to the cytosol following apoptotic induction, binds and degrades the inhibitor of apoptosis protein, XIAP in mammals, activating the caspase cascade. This study characterizes the expression of Drosophila HtrA2/OMI, a mitochondrial protein, its processing by Rhomboid-7 and demonstrates its pro-apoptotic function. Following exposure to apoptotic stress, dOMI is secreted from mitochondria and its expression profile displays an increase in a cleaved form consistent with Rhomboid-7 processing. dOMI expression resulted in sensitization of cells to apoptotic stress, observed through an increase in caspase activity. These data further validate the use of Drosophila in the study of mitochondrial driven apoptosis while implicating a potential role for Rhomboid-7 in apoptosis through proteolytic cleavage of dOMI.

While mitochondria are traditionally associated with energy production, recent studies identified its function in controlling the onset of apoptosis. Mitochondrial apoptotic control results from sequestering pro-apoptotic proteins, which are secreted following cellular stress. HtrA2/OMI is secreted from mitochondria to the cytosol following apoptotic induction, binds and degrades the inhibitor of apoptosis protein, XIAP in mammals, activating the caspase cascade. This study characterizes the expression of Drosophila HtrA2/OMI, a mitochondrial protein, its processing by Rhomboid-7 and demonstrates its pro-apoptotic function. Following exposure to apoptotic stress, dOMI is secreted from mitochondria and its expression profile displays an increase in a cleaved form consistent with Rhomboid-7 processing. dOMI expression resulted in sensitization of cells to apoptotic stress, observed through an increase in caspase activity. These data further validate the use of Drosophila in the study of mitochondrial driven apoptosis while implicating a potential role for Rhomboid-7 in apoptosis through proteolytic cleavage of dOMI.

Ultraviolet (UV) radiation has several effects on human health as well as other biological and chemical systems. The radiation can be weighted with the erythemal action spectrum and then converted to the dimensionless UV Index, which is designed to indicate the detrimental 'sunburning power' of the radiation for public heath purposes. A global view of the erythemally weighted irradiance from the Ozone Monitoring Instrument (OMI) on board the Aura spacecraft has been available since July, 2004. However, ground-based validation and correction of the satellite data are still required. In this thesis, the erythemal dose rates at local solar noon taken from the satellite were compared to ground-based data measured by spectroradiometers or broadband radiometers in two different climate areas: the Tropics and midlatitudes. This seeks to redress the lack of data and satellite validation for the Tropics, and also allows comparison with previous work in midlatitudes. The validation results show that the satellite data overestimates the ground-based data by 9%-32% at the cleanest site, with a much higher discrepancy at polluted sites. Using a radiative transfer model confirmed that the positive bias in the satellite data was mainly caused by aerosol absorption that is not taken into account in the satellite retrieval algorithm. Therefore, two empirical methods were introduced in order to correct the OMI UV data for absorbing aerosols under clear sky conditions. These methods required aerosol optical depth and aerosol single scattering, or aerosol absorption optical depth, as input parameters. The methods improved the OMI UV data by up to 30% depending on site and input data source. For cloudy conditions aerosol data is usually not available either from ground-based or satellite-based measurements; however, the effect of cloud is usually far greater than that of aerosol, and some of the aerosol effect (scattering) is intrinsically included in the cloud correction. A further empirical model for cloudy conditions was derived to reduce bias of the OMI UV data with respect to ground-based data. The method only requires the OMI UV data as an input. The cloudy model reduced the bias by about 13%-30% depending on site, and gave similar results even when used with clear sky data. Since ground-based data is sparse, the final goal of the work was to produce a corrected map of UV index for the whole of Thailand, based only on data available from satellite, which gives full regional coverage. Issues with availability and quality of satellite data meant that the best results were achieved by using only the cloudy sky correction, for all conditions. The resulting daily noontime UV Index maps of Thailand were assessed against ground-based data for independent years. The corrected UV Index was within ±2 compared with ground-based data for all sites, compared to discrepancies of up to 4 UV Index for uncorrected data.

Omi, also known as HtrA2, is a mammalian pro-apoptotic mitochondrial protein and a member of the HtrA (high temperature requirement A) family of serine proteases. Omi promotes the caspase-dependent apoptotic pathway through cleavage of IAPs (inhibitor of apoptosis proteins); this cleavage inactivates IAPs and facilitates caspase activity. Omi's proteolytic activity is necessary and essential for its pro-apoptotic function. This study is aimed to further understand the role of Omi in the cytoplasm by using the yeast two-hybrid system to identify novel Omi interactors/substrates. A HeLa (cervical carcinoma cell line) cDNA library was screened using Omi as a "bait" protein. One of the proteins indentified in this screen as a strong Omi interactor was the S5a protein and was selected for further analysis. S5a is a soluble cytosolic mammalian protein and a component of the proteasome's 19S regulatory subunit. The proteasome is a large cytosolic protein complex responsible for the controlled degradation of damaged or denatured cellular proteins. Further characterization of the interaction through an in vitro proteolytic assay demonstrated that Omi can cleaves recombinant S5a protein. This data suggests that S5a is a bona fide substrate of Omi that is degraded upon induction of apoptosis. It also provides a new mechanism that leads to the inactivation of the proteasome during cell death.

Omi/HtrA2 is a mitochondrial serine protease with high homology to the bacterial HtrA proteins. Omi promotes caspase-dependent apoptosis by binding and degrading IAPs-inhibitor of apoptosis proteins. Omi can also induce caspase-independent apoptosis but the actual mechanism is still unknown. IAP's are not the only substrates cleaved by Omi. There are at least two more known substrates of Omi, the HAX-1 and the ped/pea-15 proteins. HS1-associated protein X-1 (HAX-1) is a mitochondrial protein, degraded by Omi after induction of caspase-dependent apoptosis. Ped/pea-15 is also an anti-apoptotic protein and is cleaved by Omi after induction of caspase-independent apoptosis. The proteolytic activity of Omi is necessary and essential for its pro-apoptotic function. Recent studies suggest the proteolytic activity of Omi is regulated by specific protein-protein interactions. Presenilin was identified to be such a regulator of Omi. It binds to the PDZ domain of Omi via its carboxy-terminus and this interaction significantly increases the proteolytic activity of the enzyme. My project was aimed to investigate the normal function of Omi in cell death and the mechanism of its regulation by isolating and characterizing novel Omi interactors. I screened a human melanocyte cDNA library using the yeast-two-hybrid system and Omi as the "bait" protein. Human Rad21 protein was isolated as a specific novel interactor of Omi. Human Rad21 interacted with the PDZ domain of Omi, the part of the protein known to be involved in protein-protein interactions. Human Rad21 is a nuclear protein that plays a role in DNA double-strand break repair and sister chromatid cohesion during metaphase. Several reports suggest hRad21 has also a role in apoptosis; it is cleaved by caspase-3 and part of the protein becomes cytoplasmic. Human Rad21 was not cleaved by Omi in vitro and therefore it is unlikely to be a substrate. When tested in a proteolytic assay Rad21 was able to increase the proteolytic activity of Omi. My work suggests a new mechanism whereby Omi and hRad21 can co-operate to induce cell death. This mechanism necessitates direct interaction of hRad21 with the PDZ domain of Omi resulting in increased proteolytic activity of the enzyme.

Human High Temperature requirement A2 (HtrA2) also known as Omi, is a serine protease located in the mitochondria with an important function in both cell survival and death. My results show the proteolytic activity of Omi/HtrA2 varies under different conditions. I characterized the optimal condition for Omi/HtrA2 protease activity using an in vitro assay system. Additionally, I identified a new allosteric regulation of Omi/HtrA2 through interaction with a specific substrate, the MUL1 protein. MUL1 is a multifunctional E3 ubiquitin ligase anchored in the outer mitochondrial membrane with domains both inside mitochondria and in the cytoplasm. The data shown here strongly supports the hypothesis that Omi/HtrA2 activity is modulated by a number of different mechanisms. Some of these conditions, such as pH or substrate denaturation might reflect the state of mitochondria under stress. It has been known that Omi/HtrA2 is a stress activated protease, but the mechanism of its regulation has not been fully elucidated. Furthermore, the allosteric regulation of Omi/HtrA2 by specific substrates, can be another mechanism that provides a feedback loop to increase the activity of the enzyme. The findings from this project contribute new information on the mechanisms of activation of Omi/HtrA2 protease. They support the hypothesis that mitochondrial stress might be involved in the regulation of Omi/HtrA2 protease.

Isoprene emissions affect human health, air quality, and the oxidative capacity of the atmosphere. Globally anthropogenic non-methane volatile organic compounds (NMVOC) emissions are lower than that of isoprene, but local hotspots are hazardous to human health and air quality. In Africa the tropics are a large source of isoprene, while Nigeria appears as a large contributor to regional anthropogenic NMVOC emissions. I make extensive use of space-based formaldehyde (HCHO) observations from the Ozone Monitoring Instrument (OMI) and the chemical transport model (CTM) GEOS-Chem to estimate and examine seasonality of isoprene emissions across Africa, and identify sources and air quality consequences of anthropogenic NMVOC emissions in Nigeria. / Earth and Planetary Sciences

OmiHtrA2 is a highly conserved mammalian serine protease that belongs to the HtrA family of proteins. Omi shares homology with the bacterially expressed heat shock protease HtrA, which functions as a protease at higher temperatures and a chaperone at lower temperatures. Additionally, Omi shares sequence similarity with the mammalian homologs L56/HtrA1 and PRSP/HtrA3. Omi was first isolated as an interacting protein of Mxi2, an alternatively spliced form of the p38 stress-activated kinase, using a modified yeast two-hybrid system. Omi localizes in the mitochondria and in response to apoptotic stimuli the mature form of this protein translocates to the cytoplasm. In the cytoplasm Omi participates in both the caspase-dependent as well as caspase-independent apoptosis. Additionally, recent studies suggest that Omi may have another unique function, maintaining homeostasis within the mitochondria. In an effort to further elucidate the function of Omi, a yeast two-hybrid screening was performed to isolate novel interacting proteins. This screening identified a novel protein (HOPS), as a specific interactor of Omi. The predicted amino acid sequence of this protein does not provide any information about its potential function in mammalian cells. However, experiments show that HOPS is cleaved in vitro by Omi. Furthermore, in response to apoptotic stimuli, HOPS is also degraded in vivo. This study suggests that HOPS could be a physiological substrate of Omi that is cleaved and removed during apoptosis.

Submitted by Programa Pos-Graduação Estudos Etnicos Africanos (posafro@ufba.br) on 2013-09-16T11:59:27Z No. of bitstreams: 1 ELMVega.pdf: 3672889 bytes, checksum: e368f1682afcb523498fe4b25d53288e (MD5) / Approved for entry into archive by Hozana Azevedo (hazevedo@ufba.br) on 2017-08-11T19:02:41Z (GMT) No. of bitstreams: 1 ELMVega.pdf: 3672889 bytes, checksum: e368f1682afcb523498fe4b25d53288e (MD5) / Made available in DSpace on 2017-08-11T19:02:41Z (GMT). No. of bitstreams: 1 ELMVega.pdf: 3672889 bytes, checksum: e368f1682afcb523498fe4b25d53288e (MD5) / Neste trabalho analisei as relações de poder em um terreiro de candomblé na área metropolitana da cidade do Salvador. Através da etnografia, discorri sobre sua estrutura física, social, ritual e as formas pelas quais o grupo consolidou suas estruturas para a sua existência, através da categoria “necessidade”, na construção dos mecanismos de hierarquia e subordinação, a partir de um conceito central de Drama Social proposto por Vitor Turner, na tentativa de se buscar um desfecho para os conflitos latentes e aparentes após a sua fundação. / In this work we analyzed the relations of power in a yard of Candomblé in the metropolitan area of Salvador. Through ethnography, I discussed about its physical, social, ritual and the ways in which the group has consolidated its structures for their existence, through the category of "necessity", in the construction of the mechanisms of hierarchy and subordination from a central concept of drama Social proposed by Victor Turner, in an attempt to seek an outcome of frozen conflicts and apparent after its founding. / Centro de Estudos Afro-Orientais