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Appl. Environ. Microbiol., Jun 1996, 1951-1957, Vol 62, No. 6
RJ Gouka, PJ Punt, JG Hessing and CA van den Hondel
A study was carried out to obtain more insight into the parameters that
determine the secretion of heterologous proteins from filamentous fungi. A
strategy was chosen in which the mRNA levels and protein levels of a number
of heterologous genes of different origins were compared. All genes were
under control of the Aspergillus awamori 1,4- beta-endoxylanase A (exlA)
expression signals and were integrated in a single copy at the A. awamori
pyrG locus. A Northern (RNA) analysis showed that large differences
occurred in the steady-state mRNA levels obtained with the various genes;
those levels varied from high values for genes of fungal origin (A. awamori
1,4-beta-endoxylanase A, Aspergillus niger glucoamylase, and Thermomyces
lanuginosa lipase) to low values for genes of nonfungal origin (human
interleukin 6 and Cyamopsis tetragonoloba [guar] alpha-galactosidase). With
the C. tetragonoloba alpha-galactosidase wild-type gene full-length mRNA
was even undetectable. Surprisingly, small amounts of full-length mRNA
could be detected when a C. tetragonoloba alpha-galactosidase gene with an
optimized Saccharomyces cerevisiae codon preference was expressed. In all
cases except human interleukin 6, the protein levels corresponded to the
amounts expected on basis of the mRNA levels. For human interleukin 6, very
low protein levels were observed, whereas relatively high steady-state mRNA
levels were obtained. Our data suggest that intracellular protein
degradation is the most likely explanation for the low levels of secreted
human interleukin 6.
Copyright © 1996, American Society for Microbiology
Analysis of heterologous protein production in defined recombinant Aspergillus awamori strains
TNO Nutrition and Food Research Institute, Department of Molecular Genetics and Gene Technology, Rijswijk, The Netherlands.
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