Thiamine‐regulated gene expression of Aspergillus oryzae thiA requires splicing of the intron containing a riboswitch‐like domain in the 5′‐UTR

Abstract

Exogenous thiamine regulates Aspergillus oryzae thiA, which is involved in thiamine synthesis. One of the two introns in its 5P P-untranslated region (5P P-UTR) contains motifs (regions A and B) highly conserved among fungal thiamine biosynthesis genes. Deletion of either region relieved the repression by thiamine and thiamine inhibited intron splicing, suggesting that regions A and B are required for e⁄cient splicing. Furthermore, transcript splicing was essential for thiA gene expression. These observations suggest a novel gene expression regulatory mechanism in ¢lamentous fungi, in which exogenous thiamine controls intron splicing to regulate gene expression. Interestingly, regions A and B constitute a part of a thiamine pyrophosphate-binding riboswitch-like domain that has been quite recently found in the 5P P-UTR of thiA.

Novel metabolism in Chlamydomonas through the lens of genomics

“…Several of the thiamine biosynthetic genes in Chlamydomonas appear to contain regions that are highly similar to TPP riboswitches [53,54,55]. These regulatory elements are structures within the mRNA of individual genes that specifi cally bind TPP, and in so doing regulate the expression of the cognate gene.…”

The Promoter Activity of Isovaleryl-CoA Dehydrogenase-Encoding Gene (ivdA) fromAspergillus oryzaeIs Strictly Repressed by Glutamic Acid

“…Therefore it is strongly suggested that the ivdA and putative mccB gene own the promoter region jointly. To confirm this suggestion, we cloned this 377 bp predicted common promoter region into the SmaI site of pNG1 4) in the same and the opposite direction to uidA (Escherichia coliglucronidase gene using BKL Kit, Takara Bio, Ohtsu, Japan), to construct pNGIVF and pNGIVR respectively (Fig. 1B).…”

TPP riboswitch characterization in Alishewanella tabrizica and Alishewanella aestuarii and comparison with other TPP riboswitches

“…Riboswitches are one of the most important RNA regulatory elements known for their unique characteristics in specific and selective binding to cellular metabolites such as amino acids and derivatives (Rodionov et al, 2003), carbohydrates (Winkler et al, 2004), nucleobases and their derivatives (Nelson et al, 2015), ions (Furukawa et al, 2015) and coenzymes such as thiamine pyrophosphate (TPP) (Winkler et al, 2002;Kubodera et al, 2003). TPP as an active form of thiamine is a cofactor playing an important role in several enzymatic reactions including glycolysis, the citric acid cycle and the pentose phosphate pathway.…”

“…Later, it was revealed that some representatives of TPP riboswitch also exist in eukaryotes including fungi (in Aspergillus oryzae thiA gene (Kubodera et al, 2003)), as well as plants (Oryza sativa 3 UTR of a putative thiC gene (Sudarsan et al, 2003)), the tomato LeTHIC transcript (Zhao et al, 2011), A. thaliana (Thore et al, 2008), and the algae Chlamydomonas reinhardtii thi4 and thiC transcripts (Croft et al, 2007). The gene regulation mechanisms were studied for eukaryotic TPP riboswitches that controls intron splicing (Kubodera et al, 2003) involving long distance base pairing in Neurospora crassa (Li and Breaker, 2013). Structural studies were carried out on the crystallographic structure of TPP riboswitch in thiM mRNA (Serganov et al, 2006; and Arabidopsis thaliana (Thore et al, 2008).…”