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 assess thyroid hormone receptor (TR)-mediated activation of transcription in yeast in the presence or absence of thyroid hormone (T3), we developed a co-expression system using a TR-beta 1 expression vector and a reporter plasmid containing a 16 base pair palindromic thyroid hormone response element (TRE) upstream from a proximal CYC1 promoter that was fused to the beta-galactosidase lac Z gene of Escherichia coli. Although TR-beta 1 functions as a repressor in most mammalian systems, using our system we observed a unique thyroid hormone-independent transcriptional response indicating that wild TR-beta 1 acted as a constitutive activator in yeast; the addition of 1 microM T3 induced a moderate but significant (p less than 0.01) 25-40% further increase in transcriptional activity. Using a series of rat TR-beta 1 mutant constructs, we found that deletion of domain D and portions of E completely eliminated transcriptional activity, whereas truncations of domain F and E permitted a partial (20-40%) response compared to wild TR-beta 1 in the presence or absence of T3. These observations indicate that TR-beta 1 functions as an activator in yeast and that domains D,E and F play important interactive roles in its hormone-independent gene activation with the D domain likely being the most essential. Furthermore, our results suggest that the different transcriptional property of TR-beta 1 in yeast compared to mammalian cells i.e. activator vs repressor function, is likely determined by transcriptional factor differences which are dependent upon cellular origin.
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PMID:Rat liver c-erb A beta 1 thyroid hormone receptor is a constitutive activator in yeast (Saccharomyces cerevisiae): essential role of domains D,E and F in hormone-independent transcription. 165 14