Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To determine whether the 70-kilodalton heat shock proteins of Saccharomyces cerevisiae play a role in regulating their own synthesis, we studied the effect of overexpressing the SSA1 protein on the activity of the SSA1 5'-regulatory region. The constitutive level of Ssa1p was increased by fusing the SSA1 structural gene to the GAL1 promoter. A reporter vector consisting of an SSA1-lacZ translational fusion was used to assess SSA1 promoter activity. In a strain producing approximately 10-fold the normal heat shock level of Ssa1p, induction of beta-galactosidase activity by heat shock was almost entirely blocked. Expression of a transcriptional fusion vector in which the CYC1 upstream activating sequence of a CYC1-lacZ chimera was replaced by a sequence containing a heat shock upstream activating sequence (heat shock element 2) from the 5'-regulatory region of SSA1 was inhibited by excess Ssa1p. The repression of an SSA1 upstream activating sequence by the SSA1 protein indicates that SSA1 self-regulation is at least partially mediated at the transcriptional level. The expression of another transcriptional fusion vector, containing heat shock element 2 and a lesser amount of flanking sequence, is not inhibited when Ssa1p is overexpressed. This suggests the existence of an element, proximal to or overlapping heat shock element 2, that confers sensitivity to the SSA1 protein.
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PMID:Self-regulation of 70-kilodalton heat shock proteins in Saccharomyces cerevisiae. 218 Dec 81

Transcription of SSA1 (formerly YG100), a member of the hsp70 gene family in Saccharomyces cerevisiae, increases dramatically upon heat shock. An expression vector in which the promoter of SSA1 is fused to the Escherichia coli galactokinase gene (galK) was constructed and transformed into a galactokinase-deficient yeast strain. The transformants grew on galactose at 23 degrees C, but increased expression of the SSA1-galK fusion gene inhibited growth of cells on galactose at 37 degrees C. Selection for survivors under nonpermissive conditions yielded a class of mutants, termed HSR (for heat shock regulation), which showed reduced levels of expression of the hsp70-galK gene fusion as determined by measurement of galactokinase activity. Similar effects on beta-galactosidase activity were obtained when an SSA1-lacZ fusion vector was introduced into the mutants, suggesting action in trans through the SSA1 promoter. Analysis of Northern (RNA) blots demonstrated that the reduction in expression was a result of decreased mRNA levels for the fusion gene. In addition, mRNA levels of the endogenous SSA1 gene are reduced in an HSR mutant. Genetic analysis has shown that these mutations act in trans and affect both transcription from the SSA1 promoter and turnover of the fusion transcript. These are the first trans-acting mutations known to affect directly the transcriptional regulation and transcript stability of heat shock genes in eucaryotes.
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PMID:Isolation of mutations that act in trans to alter expression from a yeast hsp70 promoter. 314 11

Eukaryotic mRNA molecules have a 5' cap structure that is recognized by the cap-binding component of translation initiation factor eIF-4F during protein synthesis. In the budding yeast Saccharomyces cerevisiae this cap-binding protein is encoded by the CDC33 gene. We report here that decreased global translation initiation in cdc33 mutant cells has virtually no effect on the translation of mRNA from the SSA1-lacZ chimeric gene, comprised of yeast SSA1 hsp70 gene transcription and translation initiation sequences fused in-frame to the bacterial lacZ gene. When global translation initiation was limited in cdc33 mutant cells, Ssa1-LacZ polypeptide synthesis was increased relative to total protein synthesis, and the beta-galactosidase activity of the Ssa1-LacZ fusion protein was induced to wild-type levels. The normal rate of Ssa1-LacZ polypeptide synthesis in mutant cells was maintained by normal levels of SSA1-lacZ mRNA. Furthermore, in cdc33 mutant cells, the size of polysomes containing SSA1-lacZ mRNA was unaffected, while polysomes containing other specific mRNAs were smaller. Efficient Ssa1-LacZ polypeptide synthesis was also seen during eIF-4F limitation produced by disruption of the TIF4631 gene, encoding the large eIF-4F subunit. All of these findings indicate efficient SSA1-lacZ mRNA usage under conditions of globally impaired translation initiation due to eIF-4F limitation.
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PMID:Efficient translation of an SSA1-derived heat-shock mRNA in yeast cells limited for cap-binding protein and eIF-4F. 770 Feb 35

A family of highly-conserved 70 kDa stress proteins is localized in various intracellular compartments of Saccharomyces cerevisiae. Their gene expression is specifically and/or sometimes cooperatively regulated at the transcriptional level by cis-acting elements found in their respective promoters. Here, we find that depletion of cytosolic Ssa1p induced BiP(Kar2p) in the endoplasmic reticulum at the transcriptional level. By analyzing internal deletion mutants of the KAR2 promoter, we determined that the heat shock element (HSE) is necessary for KAR2 gene induction in response to the depletion of Ssa1p. Furthermore, either the KAR2HSE or SSA1HSE is sufficient for gene activation, as assayed using HSE-CYC1-lacZ fusion reporter plasmids. Finally, temperature-sensitive ssa1 mutants transformed with an HSE-CYC1-lacZ fusion vector exhibited strong induction of beta-galactosidase activity when shifted to a restrictive temperature. These results show that loss of functional Ssa1p from the cytosol up-regulates KAR2 gene expression through an HSE-mediated pathway and also support the idea that SSA1 gene expression is autoregulated.
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PMID:Saccharomyces cerevisiae KAR2 (BiP) gene expression is induced by loss of cytosolic HSP70/Ssa1p through a heat shock element-mediated pathway. 913 28

We have found that the guanine nucleotide exchange factor for ras, Cdc25p, interacts with Ssa1p in Saccharomyces cerevisiae. This interaction was observed with GST-fused Cdc25p polypeptides and confirmed by coimmunoprecipitation with the endogenous Cdc25p. Hsp82 appeared also to be co-immunoprecipitated with Cdc25p, albeit to a lower level than Hsp70. In a strain deleted for SSA1 and SSA2, we observed a reduced cellular content of Cdc25p. Consistent with a reduced activity of the cAMP-dependent PKA pathway, the rate of accumulation of both trehalose and glycogen was stimulated in the ssa-deleted strain. Expression of SSA1 reversed these effects, whereas co-expression of SSA1 and PDE2 restored high accumulation. The expression of genes repressed by cAMP, GAC1 and TPS1, fused to beta-galactosidase, was also stimulated by deletion of SSA genes. The effect of ssa deletion on glycogen accumulation was lost in a strain deleted for CDC25 rescued by the RAS2ile152 allele. Altogether, these results lead to the conclusion that Ssa1p positively controls the cAMP pathway through Cdc25p. We propose that this connection plays a critical role in the adaptation of cells to stress conditions.
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PMID:Ssa1p chaperone interacts with the guanine nucleotide exchange factor of ras Cdc25p and controls the cAMP pathway in Saccharomyces cerevisiae. 1009 33

Using a yeast two-hybrid system to search for proteins interacting with Ro52 autoantigen, we identified a novel protein-protein interaction. Two different cDNA clones, which interacted with Ro52 in the yeast two-hybrid system, were identified and isolated from a human B-cell library. Surprisingly, both clones encoded the heavy chain of human IgG1. The expression of both HIS3 and beta-galactosidase reporter genes in yeast suggested that the interaction between Ro52 and IgG occurred in vivo. In vitro studies utilizing recombinant Ro52 and purified immunoglobulins indicated that the interaction was immunoglobulin class and subclass specific. Ro52 interacted with IgG1 and IgG4, but not with IgG2, IgG3, IgA or IgM. Ro52 could also precipitate IgG directly from serum. The identified cDNA clones did not include the variable region of IgG, which suggested a non-classical interaction independent of antibody specificity. We further mapped the domain of Ro52 responsible for this interaction to the C-terminus rfp-like region. In conclusion, our data support an unusual interaction between native Ro52 and IgG. The potential biological significance of this unusual protein-protein interaction is discussed.
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PMID:Protein-protein interactions between native Ro52 and immunoglobulin G heavy chain. 1035 73