Constructing a novel expression system by specific activation of amylase expression pathway in Penicillium

Heterochromatin Protein Activates the Amylase Expression Pathway and Its Application to Recombinant Protein Expression in Penicillium oxalicum

Remodelling regulatory pathways to directionally increase the efficiency of specific promoters in chassis cells is an effective strategy for the rational construction of expression systems. However, the repeated utilization of one regulator to modify the host cell to improve expression motif efficiency has a limited effect. Therefore, it is preferable to identify new regulatory factors to activate specific pathways and thus further improve the efficiency of target elements. Heterochromatin protein 1 (HP1) is considered a main factor responsible for heterochromatin maintenance; it binds DNA and thus forms a tight structure to repress gene expression in fungi. This study revealed that the overexpression of HepA (a homologue of HP1) increased amylase expression in Penicillium oxalicum. Furthermore, HepA was overexpressed in two engineered strains in which the endoglucanase TaEG and amylase Amy15B were recombinantly expressed under the control of the amylase promoter Pamy15A, resulting in increased production of these two enzymes. Therefore, HepA could be used as a novel facilitator to modify Penicillium chassis cells, in which the efficiency of expression motifs located in the amylase pathway can be further strengthened.

Recent advances in genetic engineering to enhance plant-polysaccharide-degrading enzyme expression in Penicillium oxalicum: A brief review

With the depletion of non-renewable fossil fuels, there has been an increasing emphasis on renewable biomass. Penicillium oxalicum is notable for its exceptional capacity to secrete a diverse array of enzymes that degrade plant polysaccharides into monosaccharides. These valuable monosaccharides can be harnessed in the production of bioethanol and other sustainable forms of energy. By enhancing the production of plant-polysaccharide-degrading enzymes (PPDEs) in P. oxalicum, we can optimize the utilization of plant biomass. This paper presents recent advances in augmenting PPDE expression in P. oxalicum through genetic engineering strategies involving protoplast preparation, transformation, and factors influencing PPDE gene expression.

An impact of N-glycosylation on biochemical properties of a recombinant α-amylase from Bacillus licheniformis

Amylases are enzymes that are known to hydrolyze starch. High efficiency of amylolytic enzymes allows them to compete in the industry with the technology of chemical hydrolysis of starch. A Bacillus licheniformis strain with high amylolytic activity was isolated from soil and designated as T5. The gene encoding α-amylase from B. licheniformis T5 was successfully expressed in both Escherichia coli (rAmyT5-E) and Pichia pastoris (as rAmyT5-P). According to the study, the recombinant α-amylases rAmyT5-E and rAmyT5-P exhibited the highest activity at pH 6.0 and temperatures of 70 and 80 °C, respectively. Over 80% of the rAmyT5-E enzyme activity was preserved following incubation within the pH range of 5-9; the same was true for rAmyT5-P after incubation at pH 6-9. N-glycosylation reduced the thermal and pH stability of the enzyme. The specific activity and catalytic efficiency of the recombinant AmyT5 α-amylase were also diminished by N-glycosylation.

The interaction between the histone acetyltransferase complex Hat1-Hat2 and transcription factor AmyR provides a molecular brake to regulate amylase gene expression

The chromatin structure is generally regulated by chromatin remodelers and histone modifiers, which affect DNA replication, repair, and levels of transcription. The first identified histone acetyltransferase was Hat1/KAT1, which belongs to lysine (K) acetyltransferases. The catalytic subunit Hat1 and the regulatory subunit Hat2 make up the core HAT1 complex. In this study, the results of tandem affinity purification and mass spectrometry and bimolecular fluorescence complementation proved that the Penicillium oxalicum PoHat1-Hat2 is the transcriptional cofactor of the sequence-specific transcription factor PoAmyR, a transcription activator essential for the transcription of amylase gene. ChIP-qPCR results demonstrated that the complex PoHat1-Hat2 is recruited by PoAmyR to the promoters of prominent amylase genes Poamy13A and Poamy15A and performs histone H4 lysine12 acetylation. The result of the yeast two-hybrid test indicated that PoHat2 is the subunit that directly interacts with PoAmyR. PoHat1-Hat2 acts as the molecular brake of the PoAmyR-regulating transcription of amylase genes. A putative model for amylase gene regulation by PoAmyR-Hat2-Hat1 was constructed. Our paper is the first report that the Hat1-Hat2 complex acts as a cofactor for sequence-specific TF to regulate gene expression and explains the mechanism of TF AmyR regulating amylase genes expression.

Anticancer Asparaginases: Perspectives in Using Filamentous Fungi as Cell Factories

The enzyme L-asparaginase (L-asparagine amidohydrolase) catalyzes the breakdown of L-asparagine into aspartate and ammonia, which leads to an anti-neoplastic activity stemming from its capacity to deplete L-asparagine concentrations in the bloodstream, and it is therefore used in cases of acute lymphoblastic leukemia (ALL) to inhibit malignant cell growth. Nowadays, this anti-cancer enzyme, largely produced by Escherichia coli, is well established on the market. However, E. coli L-asparaginase therapy has side effects such as anaphylaxis, coagulation abnormality, low plasma half-life, hepatotoxicity, pancreatitis, protease action, hyperglycemia, and cerebral dysfunction. This review provides a perspective on the use of filamentous fungi as alternative cell factories for L-asparaginase production. Filamentous fungi, such as various Aspergillus species, have superior protein secretion capacity compared to yeast and bacteria and studies show their potential for the future production of proteins with humanized N-linked glycans. This article explores the past and present applications of this important enzyme and discusses the prospects for using filamentous fungi to produce safe eukaryotic asparaginases with high production yields.

Construction of a novel filamentous fungal protein expression system based on redesigning of regulatory elements

Filamentous fungi are extensively used as an important expression host for the production of a variety of essential industrial proteins. They have significant promise as an expression system for protein synthesis due to their inherent superior secretory capabilities. The purpose of this study was to develop a novel expression system by utilizing a Penicillium oxalicum strain that possesses a high capacity for protein secretion. The expression of glycoside hydrolases in P. oxalicum was evaluated in a cleaner extracellular background where the formation of two major amylases was inhibited. Four glycoside hydrolases (CBHI, Amy15B, BGL1, and Cel12A) were expressed under the highly constitutive promoter PubiD. It was found that the proteins exhibited high purity in the culture supernatant after cultivation with starch. Two inducible promoters, Pamy15A and PempA, under the activation of the transcription factor AmyR were used as elements in the construction of versatile vectors. When using the cellobiohydrolase CBHI as the extracellular quantitative reporter, the empA promoter screened from the AmyR-overexpressing strain was shown to be superior to the amy15A promoter based on RNA-sequencing data. Therefore, we designed an expression system consisting of a cleaner background host strain and an adjustable promoter. This system enables rapid and high-throughput evaluation of glycoside hydrolases from filamentous fungi.Key points• A new protein expression system derived from Penicillium oxalicum has been developed.• The expression platform is capable of secreting recombinant proteins with high purity.• The adjustable promoter may allow for further optimization of recombinant protein synthesis.