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Figure 1 | Microbial Cell Factories

Figure 1

From: The HAC1 gene from Pichia pastoris: characterization and effect of its overexpression on the production of secreted, surface displayed and membrane proteins

Figure 1

The unfolded protein response in the yeast S. cerevisiae. Under normal conditions Ire1p is present in the ER membrane as a monomer in association with Kar2/Bip. Upon ER stress, in a first step, Kar2 dissociates from Ire1p which causes clustering of Ire1p in the ER membrane. In a second step, direct interaction of the unfolded protein with a stress sensing region of the Ire1p orients the cytosolic effector domains [4]. Clustering causes transautophosphorylation of the kinase domain (K) and simultaneous activation of the endoribonuclease (R) activity. Activation of Ire1p initiates an unconventional mRNA splicing reaction, which removes an intron from a unique mRNA species, HAC1, which encodes for an active transcription factor. Hac1p activates target genes coding for chaperones, foldases, lipid synthesis etc.

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