5 research outputs found
Immune response and functional role of antibodies raised in heifers against a Staphylococcus aureus CP5 lysate and recombinant antigens vaccine formulated with Iscom Matrix adjuvant
No full textStaphylococcus aureus is the most frequently isolated pathogen from bovine intramammary infections worldwide. Commercially available vaccines for mastitis control are composed either of S. aureus lysates or inactivated whole-cells formulated with traditional adjuvants. We recently showed the ability of a S. aureus CP5 lysate vaccine adjuvanted with Iscom Matrix to generate a longer lasting specific antibody response in blood and milk, with improved opsonic capacity, compared with a S. aureus CP5 whole-cell formulation. The aim of the present study was to obtain an experimental immunogen composed of lysed cells of a CP5 S. aureus strain supplemented with recombinant clumping factor A, fibronectin binding protein A and -toxin formulated with Iscom Matrix, characterize the immune response generated when immunizing pregnant heifers and assess the functional role of antibodies raised against this immunogen in experimental models. Both a lysate vaccine and a lysate + recombinant antigens vaccine elicited antibodies that promoted neutrophil phagocytosis and inhibited internalization into mammary epithelial cells, in vitro. Incorporation of defined antigenic molecules to the lysate formulation elicited a strong specific humoral immune response against both lysate and recombinant antigens and was associated with higher expression of regulatory and pro-inflammatory cytokines. In addition, antibodies were efficient for blocking S. aureus binding to bovine fibrinogen and fibronectin, and neutralizing -toxin effect in vitro, placing these antigens as candidates to be included in a formulation directed to prevent staphylococcal bovine mastitis.Fil: Camussone, Cecilia María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Pujato, Nazarena. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Tecnología Inmunológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Renna, Maria Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Cs.veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Veaute, Carolina Melania Isabel. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Tecnología Inmunológica; ArgentinaFil: Morein, B.. Uppsala University. Department of Clinical Virology; SueciaFil: Marcipar, Ivan Sergio. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Tecnología Inmunológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Calvinho, Luis Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Cs.veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; Argentin
Author response: Srs2 promotes synthesis-dependent strand annealing by disrupting DNA polymerase δ-extending D-loops
No full textHelicases and DNA dependent ATPases of Sulfolobus solfataricus
No full textElectronic version does not contain associated previously published materialDNA is susceptible to various types of damage as a result of normal cellular metabolism or from environmental sources. In order to maintain genome stability a number of different, partially overlapping DNA repair pathways have evolved to tackle specific lesions or distortions in the DNA. Nucleotide excision repair (NER) is highly conserved throughout eukarya, bacteria and archaea and predominantly targets lesions that result from exposure to UV light, for example cyclobutane pyrimidine dimers and 6-4 photoproducts. The majority of archaea possess homologous of the eukaryotic repair genes and this thesis describes the isolation and the characterization of two XPB homologues identified in the crenarchaeon Sulfolobus solfataricus, SsoXPB1 and SsoXPB2.
Human XPB is one of 10 proteins that make up the TFIIH transcription complex. The activity of XPB is tightly controlled by protein interactions, in particular with p52, which stimulates the ATPase activity of XPB. Rather than a conventional helicase, human XPB is thought to act as an ATP dependent conformational switch. Consistent with human XPB, however, the S. solfataricus proteins were unable to catalyse strand separation and the identification of an archaeal protein partner, Bax1, for SsoXPB2 was one of the focuses of this project.
In order to maintain genome stability, the DNA must be replicated accurately with each cell cycle. When the advancing replication fork stalls at a lesion or a DNA break, it is crucial that the fork is reset and that replication continues to completion. The helicase Hel308 is thought to clear the lagging strand template of a stalled replication fork in order for replication restart to proceed via homologous recombination (HR). Although the specific function of Hel308 is not well understood, the possibilities are described in this thesis.
Strand exchange proceeds to form a D-loop, followed by branch migration to increase regions of heterology during the synapsis stage of HR. No motors for branch migration have previously been recognised in archaea, although the identification of a possible candidate was investigated during this project
Isolation and characterization of "Arabidopsis" mutants with altered homologous recombination levels : a new function for an INO80 SWI/SNF ATPase
No full textHomologous recombination (HR) in eukaryotic organisms serves a dual role in providing
genetic flexibility by creating novel sequence assortments upon meiosis and in maintaining
genome integrity through DNA repair in somatic tissues. HR represents an alternative
pathway to non-homologous end-joining (NHEJ) for the repair of double-strand breaks
(DSB). The repair by NHEJ may not preserve the integrity of the genetic information
whereas the HR pathway is more faithful. The choice of a pathway to repair DSBs is thus
crucial for genome integrity and evolution, especially in plants where the germline is only
determined late during development. Very little is known on what influences the choice of
the pathway taken, but chromatin structure at the site of a lesion likely will play a major
role in the recruitment of repair enzymes and thereby the choice of repair pathway. As a
consequence, various proteins that are not part of the core of the recombination machinery
may directly participate in the regulation of HR. At the time this work was initiated, no
plant gene involved in the HR pathway or its regulation was characterized yet. As plants
are powerful genetic tools especially for screening, we decided on designing and
conducting a genetic screen to identify plant genes involved in HR.
Here I describe a genetic screen in Arabidopsis thaliana for mutants with altered
somatic recombination levels and the characterization of the resulting mutant candidates.
For the screen, I used a stably integrated luciferase based intrachromosomal HR substrate
and a T-DNA construct designed for activation tagging as a mutagenic agent. Out of 19520
individual transformants tested, 37 exhibited an altered HR phenotype. Nine of them were
sterile and/or exhibited important developmental or growth phenotypes that precluded the
formation of progeny seeds, which is more than the average number of sterile plants
expected. However, in most cases the altered recombination phenotype was lost in the
offspring. To characterize the mutations, I cloned all the T-DNA insertion sites by plasmid
rescue and determined the potential target genes. I discuss the genes likely to be responsible
of the observed phenotype.
Here I report the thorough analysis of a mutant in the Arabidopsis INO80 ortholog of
the SWI/SNF ATPase family, which shows a reduced frequency of HR. In contrast,
sensitivity to genotoxic agents and efficiency of T-DNA integration remain unaffected.
This suggests that INO80 is a positive regulator of HR, while not affecting other repair
pathways. Further, transcriptionaly silent TSI loci are not reactivated in absence of INO80,
suggesting that Arabidopsis INO80 function is independent of transcriptional silencing.
Using whole genome expression studies by microarray profiling I show evidence that
INO80 regulates a small subset of Arabidopsis genes, suggesting a dual role for INO80 in
transcription and repair by HR. Moreover, the recombination-promoting function of INO80
is not likely to involve general transcriptional regulation, and the transcriptional regulation
of repair related genes is unaffected in the mutant. This is the first report of INO80 function
in a higher eukaryote. Mononucleosome binding studies support the suggestion that INO80
positively regulates HR through modification of chromatin structure at sites of DNA repair
by HR. Finally, I provide evidence for the existence and/or connectivity of INO80 with
other INO80 complex partners in Arabidopsis
Genotype and phenotype characterisation of Friedreich ataxia mouse models and cells
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityFriedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder, caused by a GAA repeat expansion mutation within intron 1 of the FXN gene, resulting in reduced level of frataxin protein. Normal individuals have 5 to 40 GAA repeat sequences, whereas affected individuals have approximately 70 to more than 1000 GAA triplets. Frataxin is a mitochondrial protein involved in iron-sulphur cluster and heme biosynthesis. The reduction in frataxin expression leads to oxidative stress, mitochondrial iron accumulation and consequential cell death with the primary sites of neurons of the dorsal root ganglia and the dentate nucleus of the cerebellum. FRDA, which is the most common inherited ataxia, affecting 1:50,000 Caucasians, is characterised by neurodegeneration, cardiomyopathy, diabetes mellitus and skeletal deformities. To investigate FRDA molecular disease mechanisms and therapy, several human FXN YAC transgenic mouse models have been established: Y47R, containing normal-sized (GAA)9 repeats; YG8R and YG22R, which initially contained expanded GAA repeats of 90-190 units and 190 units, respectively, but which have subsequently been bred to now contain expanded GAA repeats of 120-220 units and 170-260 units, respectively, and YG8sR (YG8R with a small GAA band) that was recently generated from YG8R breeding. To determine the FXN transgene copy number in the enhanced GAA repeat expansion-based FRDA mouse lines, a TaqMan qPCR assay was developed. The results demonstrated that the YG22R and Y47R lines had a single copy of the FXN transgene while the YG8R line had two copies. The YG8s lines showed less than one copy of the target gene, suggesting potential deletion of the FXN gene. Single integration sites of all transgenes were confirmed by fluorescence in situ hybridisation (FISH) analysis of metaphase and interphase chromosomes. However, in the YG8s line, at least 25% of the YG8s cells had no signals, while the remaining cells showed one signal corresponding to the transgenic FXN gene. In addition, the analysis of FXN exons in YG8s rescue mice by PCR confirmed the presence of all FXN exons in these lines, suggesting the incidence of somatic mosaicism in these lines. Extended functional analysis was carried out on these mice from 4 to 12 months of age. Coordination ability of YG8R, YG8sR and YG22R ‘FRDA-like’ mice, together with Y47R and C57BL6/J wild-type control mice, was assessed using accelerating rotarod analysis. The results indicated a progressive decrease in the motor coordination of YG8R, YG22R and YG8sR mice compared to Y47R or C57BL6/J controls. Locomotor activity was also assessed using an open field beam-breaker apparatus followed by four additional functional analyses including beam-walk, hang wire, grip strength and foot print tests. The results indicated significant functional deficits in the FRDA mouse models. Glucose and insulin tolerance tests were also conducted in the FRDA mouse models, indicating glucose intolerance and insulin hypersensitivity in the aforementioned lines.
To investigate the correlation between the FRDA-like pathological phenotype and frataxin deficiency in the FRDA mouse models, frataxin mRNA and protein levels as well as somatic GAA repeat instability were examined. The results indicated that somatic GAA repeats increased in the cerebellum and brain of YG22R, YG8R and YG8sR mice, together with significantly reduced levels of FXN mRNA and protein in the liver of YG8R and YG22R compared to Y47R. However, YG8sR lines showed a significant decrease in FXN mRNA in all of the examined tissues compared to Y47R human FXN and C57BL6/J mouse Fxn mRNA. Protein expression levels were also considerably reduced in all the tissues of YG8sR mice compared to Y47R. Subsequently, the telomere length of human and mouse FRDA and control fibroblasts was assessed using qPCR and Q-FISH. The results indicated that the FRDA cells had chromosomes with relatively longer telomeric repeats in comparison to the controls. FRDA cells were screened for expression of telomerase activity using the TRAP assay and a quantitative assay for hTERT mRNA expression using TaqMan qRT-PCR. The results indicated that telomerase activity was not present in the FRDA cells. To investigate whether FRDA cells maintained their telomeres by ALT associated PML bodies (APBs), co-localisation of PML bodies with telomeres was assessed in these cells using combined immunofluorescence to PML and Q-FISH for telomere detection. The results demonstrated that the FRDA cells had significantly higher co-localised PML foci with telomeric DNA compared to the normal cells. Moreover, telomere sister chromatid exchange (T-SCE) frequencies were analysed in the human FRDA cell lines using chromosome orientation FISH (CO-FISH). The results indicated a significant increase in T-SCE levels of the FRDA cell lines relative to the controls. Furthermore, growth curve and population doubling analysis of the human FRDA and control fibroblasts was carried out. The results showed that the FRDA fibroblast cell cultures underwent growth arrest with higher cumulative population doubling compared to the controls. Though, further analysis of telomere length at different passage numbers revealed that the FRDA cells lost telomeres faster than the controls. Finally, the telomere dysfunction-induced foci (TIF) assay was performed to detect DNA damage in the human FRDA fibroblast cells using an antibody against DNA damage marker γ-H2AX and a synthetic PNA probe for telomeres. The frequency of γ-H2AX foci was significantly higher in the FRDA cells compared to the controls. Similarly, the FRDA cells had greater frequencies of TIFs in comparison to the controls, suggesting induced telomere dysfunction in the FRDA cells
