Palindrome with Spacer of One Nucleotide Is Characteristic of the cis-Acting Unfolded Protein Response Element inSaccharomyces cerevisiae

Abstract

When unfolded proteins are accumulated in the endoplasmic reticulum (ER), an intracellular signaling pathway termed the unfolded protein response (UPR) is activated to induce transcription of ER-localized molecular chaperones and folding enzymes in the nucleus. In Saccharomyces cerevisiae, at least six lumenal proteins including essential Kar2p and Pdi1p are known to be regulated by the UPR. We and others recently demonstrated that the basic-leucine zipper protein Hac1p/ Ern4p functions as a trans-acting factor responsible for the UPR. Hac1p binds directly to the cis-acting unfolded protein response element (UPRE) responsible for Kar2p induction. Moreover, we showed that the KAR2 UPRE contains an E box-like palindrome separated by one nucleotide (CAGCGTG) that is essential for its function. We report here that the promoter regions of each of five target proteins (Kar2p, Pdi1p, Eug1p, Fkb2p, and Lhs1p) contain a single UPRE sequence that is necessary and sufficient for induction and that binds specifically to Hac1p in vitro. All of the five functional UPRE sequences identified contain a palindromic sequence that has, in four cases, a spacer of one C nucleotide. This unique characteristic of UPRE explains why only a specific set of proteins are induced in the UPR to cope with ER stress.

Proteomic analysis of dimorphic transition in the phytopathogenic fungus Ustilago maydis

“…The b-regulated secreted proteins include PEP4, glutaminase A, HOM6 and protein disulphide isomerase. Protein disulphide isomerase, which catalyses the proper formation of disulphide bridges may play a role in protein secretion itself, since elevated levels of this enzyme are required in S. cerevisiae for efficient protein secretion [22]. Since secreted proteins would be expected to reside in the culture supernatant we assume that most of the identified proteins carrying a secretion signal are either still in the endoplasmatic compartment or are associated with the cell wall.…”

SCFCdc4-mediated Degradation of the Hac1p Transcription Factor Regulates the Unfolded Protein Response inSaccharomyces cerevisiae

“…The yeast unfolded protein response (UPR) involves two unique participants, the Ire1p transmembrane receptor kinase/endonuclease (Cox et al, 1993;Mori et al, 1993), and the basic leucine zipper (bZip) transcription factor Hac1p Mori et al, 1996), which transactivates genes bearing UPRE elements (Mori et al, 1992(Mori et al, , 1998Patil and Walter, 2004). HAC1 mRNA is synthesized constitutively as a precursor bearing a 252-nucleotide intron that blocks translation as the result of base pairing with a sequence in the 5Ј-untranslated region of the mRNA Kawahara et al, 1997;Ruegsegger et al, 2001).…”

“…The concentrations of these components in the ER are adjusted according to need by the unfolded protein response (UPR; Kozutsumi et al, 1988;Mori et al, 1992; for review, see Kaufman, 1999;Ma and Hendershot, 2001;Patil and Walter, 2001;Schrö der and Kaufman, 2005). The UPR regulates the transcription of ϳ5% of the open reading frames in the Saccharomyces cerevisiae genome, many of which encode proteins with functions involved in diverse processes, including protein translocation, glycosylation, folding and degradation, lipid/inositol metabolism, vesicular trafficking, vacuolar protein sorting, and cell wall biogenesis (Travers et al, 2000).The yeast unfolded protein response (UPR) involves two unique participants, the Ire1p transmembrane receptor kinase/endonuclease (Cox et al, 1993;Mori et al, 1993), and the basic leucine zipper (bZip) transcription factor Hac1p Mori et al, 1996), which transactivates genes bearing UPRE elements (Mori et al, 1992(Mori et al, , 1998Patil and Walter, 2004). HAC1 mRNA is synthesized constitutively as a precursor bearing a 252-nucleotide intron that blocks translation as the result of base pairing with a sequence in the 5Ј-untranslated region of the mRNA Kawahara et al, 1997;Ruegsegger et al, 2001).…”

Proliferation of the endoplasmic reticulum occurs normally in cells that lack a functional unfolded protein response

“…The phosphorylated Ire1p then catalyses an unconventional splicing reaction that ultimately produces mRNA for a transcription factor called Hac1p (Cox and Walter, 1996;Gonzalez et al, 1999;Shamu and Walter, 1996;Sidrauski and Walter, 1997). Hac1p stimulates transcription of several ER chaperone genes, including KAR2, thus restoring a proper balance of chaperones within the ER (Mori et al, 1996(Mori et al, , 1998. The unfolded protein response is needed to maintain appropriate chaperone levels, particularly under stress conditions.…”