Usage of an intronic promoter for stable gene expression in Saccharomyces cerevisiae

HDA-2-Containing Complex Is Required for Activation of Catalase-3 Expression in Neurospora crassa

It is essential for aerobic organisms to maintain the homeostasis of intracellular reactive oxygen species (ROS) for survival and adaptation to the environment. In line with other eukaryotes, the catalase of Neurospora crassa is an important enzyme for clearing ROS, and its expression is tightly regulated by the growth phase and various oxidative stresses. Our study reveals that, in N. crassa, histone deacetylase 2 (HDA-2) and its catalytic activity positively regulate the expression of the catalase-3 (cat-3) gene. HDA-2, SIF-2, and SNT-1 may form a subcomplex with such a regulation role. As expected, deletion of HDA-2 or SIF-2 subunit increased acetylation levels of histone H4, indicating that loss of HDA-2 complex fails to deacetylate H4 at the cat-3 locus. Furthermore, loss of HDA-2 or its catalytic activity led to dramatic decreases of TFIIB and RNA polymerase II (RNAP II) recruitment at the cat-3 locus and also resulted in high deposition of H2A.Z at the promoter and transcription start site (TSS) regions of the cat-3 gene. Collectively, this study strongly demonstrates that the HDA-2-containing complex activates the transcription of the cat-3 gene by facilitating preinitiation complex (PIC) assembly and antagonizing the inhibition of H2A.Z at the cat-3 locus through H4 acetylation. IMPORTANCE Clearance of reactive oxygen species (ROS) is critical to the survival of aerobic organisms. In the model filamentous fungus Neurospora crassa, catalase-3 (cat-3) expression is activated in response to H₂O₂-induced ROS stress. We found that histone deacetylase 2 (HDA-2) positively regulates cat-3 transcription in N. crassa; this is widely divergent from the classical repressive role of most histone deacetylases. Like HDA-2, the SIF-2 or SNT-1 subunit of HDA-2-containing complex plays a positive role in cat-3 transcription. Furthermore, we also found that HDA-2-containing complex provides an appropriate chromatin environment to facilitate PIC assembly and to antagonize the inhibition role of H2A.Z at the cat-3 locus through H4 acetylation. Taken together, our results establish a mechanism for how the HDA-2-containing complex regulates transcription of the cat-3 gene in N. crassa.

5' untranslated regions: the next regulatory sequence in yeast synthetic biology

When developing industrial biotechnology processes, Saccharomyces cerevisiae (baker's yeast or brewer's yeast) is a popular choice as a microbial host. Many tools have been developed in the fields of synthetic biology and metabolic engineering to introduce heterologous pathways and tune their expression in yeast. Such tools mainly focus on controlling transcription, whereas post-transcriptional regulation is often overlooked. Herein we discuss regulatory elements found in the 5' untranslated region (UTR) and their influence on protein synthesis. We provide not only an overall picture, but also a set of design rules on how to engineer a 5' UTR. The reader is also referred to currently available models that allow gene expression to be tuned predictably using different 5' UTRs.