Current Research
The research is focused on understanding the molecular mechanisms underlying protein secretion (and associated stresses) and the epigenetic regulation of transcription in filamentous fungi, mainly Aspergillus spp.. In addition, the research programme includes studies of weak acid preservatives and their mode of action against fungal contaminants in food (Plumridge et al., 2004).
The area of protein secretion has both basic and applied aspects (Archer, 2000; MacKenzie et al., 2004). The basic research has a focus on the stress responses that emanate from the endoplasmic reticulum (ER) (with Drs Sally Barnes, Thomas Guillemette, Adrian Watson). The unfolded protein response is initiated when proteins fold poorly within the ER and it leads to the transcriptional up-regulation of genes that either lead, as part of the response, to the synthesis of more foldases and chaperones in the ER. The extent of the response is being investigated using genomic approaches and gene arrays. Other responses initiated within the ER, and not part of the UPR, are also being investigated. In particular, we have discovered that genes encoding secreted proteins are selectively transcriptionally down-regulated following ER stress and we are currently engaged in unraveling the molecular basis of this effect (Al Sheikh et al., 2004). The group also has an interest in the regulation of translation following ER stress (with Dr Simon Avery).
The fungal expression systems (mainly Aspergillus niger and Pichia pastoris) are used to produce proteins for applications and for studies of the relationship between protein structure and function. We have a particular focus on amyloid-forming lysozyme variants (Dumoulin et al., 2003) (with Professor Chris Dobson, University of Cambridge), 2S plant allergens (Alcocer et al., 2002; Murtagh et al., 2003)(with Dr Marcos Alcocer, School of Biosciences, Nottingham) and haemoglobins (with Dr Ken Lowe).
The regulation of transcription by epigenetic processes is poorly understood in filamentous fungi. We have shown (Drs Heather Lee and Lola Montiel) that DNA can be methylated in Aspergillus spp. and that DNA methylation may be involved in dimorphism by the human pathogen Candida albicans. We are currently investigating the impact of DNA methylation on chromatin structure and functionality in these fungi.
Cited References
Alcocer, M.J.C., Murtagh, G.J., Bailey, K., Dumoulin, M., Sarabia, A., Parker, M.J. and Archer, D.B. (2002) The disulphide mapping, folding and characterisation of recombinant Ber e 1 and SFA8, two sulphur-rich 2S plant albumin allergens. Journal of Molecular Biology 324, 165-175.
Al-Sheikh, Watson, A.J., H., Lacey, G.A., MacKenzie, D.A., Jeenes, D.J., Pakula, T., Penttilä, M. and Archer, D.B. (2004) Endoplasmic reticulum stress leads to the selective transcriptional down-regulation of genes encoding secretory proteins in Aspergillus niger. Molecular Microbiology, in press.
Archer, D.B. (2000) Filamentous fungi as microbial cell factories for food use. Current Opinion in Biotechnology 11, 478-483.
Dumoulin, M., Last, A.M., Desmyter, A., Decanniere, K., Canet, D., Larsson, G., Spencer, A., Archer, D.B., Muyldermans, S., Wyns, L., Redfield, C., Matagne, A., Robinson, C.V. and Dobson, C.M. (2003) A camelid antibody fragment inhibits the formation of amyloid fibrils by human lysozyme. Nature 424, 783-788.
MacKenzie, D.A., Jeenes, D.J. and Archer, D.B. (2004) Filamentous fungi as expression systems for heterologous proteins. In: The Mycota II, Ch.15 (U. Kuck, Ed.), Springer 289- 315.
Murtagh, G.J., Archer, D.B., Dumoulin, M., Matthews, S., Arshad, S.H. and Alcocer, M.J.C. (2003) In vitro stability and immunoreactivity of the native and recombinant plant food 2S albumins Ber e 1 and SFA-8. Clinical and Experimental Allergy 33, 1147-1152.
Plumridge, A., Hesse, S.J.A., Watson, A.J., Lowe, K.C., Stratford, M. and Archer, D.B. (2004) The weak acid preservative, sorbic acid, inhibits conidial germination and mycelial growth of Aspergillus niger through intracellular acidification. Applied and Environmental Microbiology 70, 3506-3511.