Carbon catabolite repression in A. nidulans is a regulatory system which allows the organism to utilize the most preferable carbon source by repressing the expression of genes encoding enzymes utilizing alternative carbon sources. A ubiquitination pathway was shown to be one of the key mechanisms which regulate carbon source utilization, when creB was found to encode a deubiquitinating enzyme. Strains containing mutations in creB show loss of repression for some metabolic pathways in carbon catabolite repressing conditions, and also grow very poorly on several sole carbon sources such as quinate and proline, suggesting CreB plays multiple roles in the cell. This work describes the analysis of the interaction of CreB with CreA, and with PrnB and QutD. Various epitope-tagged versions of CreA were expressed in A. nidulans, and an internally located HA-epitope tag was found to allow detection of CreA using Western analysis. A diploid strain was constructed between strains containing HA-tagged CreA and FLAG-tagged CreB. When CreB was immunoprecipitated, HA-tagged CreA was also precipitated in the diploid, indicating that CreA and CreB are present in a complex in vivo. To determine whether CreA is a ubiquitinated protein, a version of CreA that was tagged with both an HA epitope and a His-tag was expressed in A. nidulans, and protein extracts were precipitated with an UbiQapture™-Q matrix. Western analysis was used to show that CreA was present in the precipitate. These findings suggest that CreA is a ubiquitinated protein, and a target of the CreB deubiquitination enzyme. To determine whether the proline permease (PrnB) is a direct substrate of CreB, plasmids to express epitope-tagged versions of PrnB were constructed and introduced into the prnB mutant strain. No tagged protein could be detected by Western analysis, even when these constructs were over-expressed from the gpdA promoter. However, a construct to express an HA epitope tagged version of quinate permease (QutD) fully complemented the qutD mutant strain, and HA-tagged QutD could be easily detected in Western analysis when probed with the anti-HA monoclonal antibody. A diploid strain was made between a complementing transformant and a strain expressing a FLAG-tagged CreB construct. When QutDHA was immunoprecipitated, CreBFLAG was detected in the immunoprecipitate of the diploid. A proportion of QutDHA was also co-precipitated in the diploid when CreBFLAG was immunoprecipitated. Thus, CreB is present in a complex with QutD in vivo. Further results showed that the concentration of QutD in the cell is lower in a creB null mutant background than in the wild-type background, indicating that deubiquitination is required to prevent protein turnover. Northern analysis of mRNA showed that the failure of creB mutant strains to grow on quinate medium was not due to a failure of transcriptional induction of qutD, as the amount of mRNA was not lower in a creB1937 mutant background compared to the wild-type. Furthermore, experiments were undertaken that showed that QutD is a ubiquitinated protein. These findings suggest that quinate permease is regulated through deubiquitination involving the CreB deubiquitination protein in A. nidulans. In addition to the candidate protein approach asking whether CreA is a substrate of CreB, a proteomics approach was also used to identify proteins that interact with CreA. However, no clear interacting proteins were identified using this approach. / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008

La larga presencia histórica de arabehablantes en la península ibérica tuvo como resultado la inclusión de préstamos léxicos, a menudo llamados arabismos, en el español. El objetivo de esta investigación ha sido comparar el uso de estos arabismos en el español cotidiano moderno con el del siglo XVI. Con este fin, se presenta una enumeración ordenada de los arabismos más frecuentes en el español moderno y se la compara con una lista correspondiente del español del siglo XVI. Las listas están basadas en dos corpus que maneja la Real Academia Española. Se realzan las semejanzas y diferencias entre las  dos listas y se discuten las posibles explicaciones de cambios en popularidad para los arabismos respectivos. Además, se presentan cálculos del porcentaje total de arabismos en el español de hoy y el del siglo XVI. Para este cálculo han sido usadas novelas de las dos épocas. Las novelas escogidas están todas arraigadas el las dos Castillas; por consiguiente, la comparación del porcentaje se limitará al español castellano. El estudio añade información cuantitativa que hasta ahora parece faltar respecto al conocimiento existente de arabismos en el español. El resultado de la investigación indica que la frecuencia de arabismos en la lengua cotidiana ha disminuido solo marginalmente desde el siglo XVI, mientras que el número de arabismos distintos en el uso corriente del español ha sufrido una reducción más pronunciada y el número de raíces hispanoárabes utilizadas ha decrecido aún más. Aproximadamente la mitad de los arabismos más frecuentes en el siglo XVI todavía mantienen esta posición; para la mayoría de los arabismos que han experimentado un aumento o reducción evidente en popularidad de uso existen explicaciones plausibles en forma de cambios en la sociedad. / The long-lasting historical presence of Arabic-speaking groups on the Iberian Peninsula resulted in various lexical loans, often referred to as arabisms, in Spanish. The objective of this investigation has been to compare the use of these arabisms in modern colloquial Spanish with that of the 16th century. For this purpose an ordered list of the most frequent arabisms found in modern Spanish is presented and compared with a similar list of arabisms found in texts from the 16th century. The lists are based on two corpus managed by the Royal Spanish Academy. Similarities and differences between the two lists are highlighted and possible explanations for the change in popularity of the respective arabisms are discussed. In addition, calculations of the total percentage of arabisms in current and 16th century Spanish are presented. Novels from the respective periods are used as a basis for these calculations. All the chosen novels are rooted in Castile; consequently, the percentage comparison is limited to Castilian Spanish. The study adds quantitative information that currently seems to be lacking to the existing knowledge of arabisms in Spanish. The result of the investigation indicates that the frequency of arabisms in colloquial language has diminished marginally since the 16th century, whereas the number of distinct arabisms in everyday usage of Spanish has suffered a more pronounced reduction and the number of hispanoarabic roots used has decreased even more. Approximately half of the most frequent arabisms in the 16th century still maintain this position; for a majority of the arabisms that have experienced an evident increase or decrease in popularity there exist plausible explanations in the form of changes in society.