The ascomycete Trichoderma reesei is used for the production of plant cell wall-degrading
enzymes in industrial scale. The interplay of the transactivator Xyr1 and the repressor Cre1 mainly
regulates the expression of these enzymes. During inducing conditions, such as in the presence of
sophorose, the transcription of the two major cellulase-encoding genes, cbh1 and cbh2, is activated as
well as the expression of xyr1. In the presence of D-glucose carbon catabolite repression mediated by
Cre1 takes place and the expression of Xyr1 and the plant cell wall-degrading enzymes is downregulated.
In this study we compare the chromatin status of xyr1, cbh1, and cbh2 promoters in the
wild-type strain and the Cre1-deficient strain Rut-C30. Chromatin rearrangement occurs in the xyr1 promoter during induction
on sophorose. Chromatin opening and protein-DNA interactions in the xyr1 promoter were detected especially in
a region located 0.9 kb upstream the translation start codon, which bears several putative Cre1-binding sites and a
CCAAT-box. Moreover, the xyr1 promoter is overall more accessible in a cre1-truncated background, no matter which
carbon source is present. This makes the xyr1 regulatory sequence a good target for promoter engineering aiming at the
enhancement of cellulase production.
Keywords: Cellulases, Chromatin, Promoter, Trichoderma reesei, Rut-C30, Xyr1.
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