title: GAP promoter library for fine-tuning of gene expression in Pichia pastoris.
abstract: A library of engineered promoters of various strengths is a useful genetic tool that enables the fine-tuning and precise control of gene expression across a continuum of broad expression levels. The methylotrophic yeast Pichia pastoris is a well-established expression host with a large academic and industrial user base. To facilitate manipulation of gene expression spanning a wide dynamic range in P. pastoris, we created a functional promoter library through mutagenesis of the constitutive GAP promoter. Using yeast-enhanced green fluorescent protein (yEGFP) as the reporter, 33 mutants were chosen to form the functional promoter library. The 33 mutants spanned an activity range between ∼0.6% and 19.6-fold of the wild-type promoter activity with an almost linear fluorescence intensity distribution. After an extensive characterization of the library, the broader applicability of the results obtained with the yEGFP reporter was confirmed using two additional reporters (β-galactosidase and methionine adenosyltransferase [MAT]) at the transcription and enzyme activity levels. Furthermore, the utility of the promoter library was tested by investigating the influence of heterologous MAT gene expression levels on cell growth and S-adenosylmethionine (SAM) production. The extensive characterization of the promoter strength enabled identification of the optimal MAT activity (around 1.05 U/mg of protein) to obtain maximal volumetric SAM production. The promoter library permits precise control of gene expression and quantitative assessment that correlates gene expression level with physiologic parameters. Thus, it is a useful toolbox for both basic and applied research in P. pastoris.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Xiulin
authors.initials: X
authors.lastname: Qin
authors.forename: Jiangchao
authors.initials: J
authors.lastname: Qian
authors.forename: Gaofeng
authors.initials: G
authors.lastname: Yao
authors.forename: Yingping
authors.initials: Y
authors.lastname: Zhuang
authors.forename: Siliang
authors.initials: S
authors.lastname: Zhang
authors.forename: Ju
authors.initials: J
authors.lastname: Chu
mesh_terms: D019677:Artificial Gene Fusion; D004252:DNA Mutational Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D015870:Gene Expression; D015723:Gene Library; D017930:Genes, Reporter; D005818:Genetic Engineering / Q000379:methods*; D005827:Genetics, Microbial / Q000379:methods*; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010843:Pichia / Q000235:genetics* / Q000502:physiology; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating)