High impact information on BAS1

• Similarly, we find that low levels of transcription by Bas1/Bas2 are TATA-independent, whereas high levels are TATA-dependent [1].
• BAS1 has an NH2-terminal region similar to those of the myb proto-oncogene family [2].
• The factor BAS1 has been shown to bind at a site containing the TGACTC hexanucleotide motif in the ADE2 and ADE5,7 promoters [3].
• Coregulation of purine and histidine biosynthesis by the transcriptional activators BAS1 and BAS2 [3].
• The transcription factors BAS1 and BAS2/PHO2, which are also regulators of the histidine pathway, participate in the regulation of the purine biosynthetic pathway [3].

Biological context of BAS1

• These results suggest that GCN4p and BAS1/2p are able to act simultaneously through the same DNA sequence in vivo and use this site independently from each other in a non-exclusive manner [4].
• Loss of BAS1 abolished or significantly reduced the repression of these genes in response to glycine removal but this phenotype was much less apparent in the absence of BAS2 or GCN4 [5].
• Sequence analysis of the promoters for the most severely repressed genes identified a conserved sequence, TGACTC, a known binding site for the transcription factors Gcn4p and Bas1p [5].
• The effect of extracellular adenine and the role of the transcriptional activator Bas1p on expression of the yeast genome was assessed by two-dimensional (2D) analysis of the yeast proteome [6].
• Adenine repression of the purine nucleotide biosynthetic genes in Saccharomyces cerevisiae involves down-regulation of the activator protein BAS1 or BAS2 by an unknown mechanism [7].

Associations of BAS1 with chemical compounds

• The maximal basal and induced expression of these purine genes requires the presence of both BAS1 and BAS2 [3].
• A number of genes, including BAS1 were required for activation by glycine but only the SHM2 gene was required for repression in the absence of glycine [5].
• Glycine withdrawal repressed many of the same genes as addition of adenine, a process known to be dependent on Bas1p [5].
• Upon limitation for purines, the SAICAR/AICAR regulatory signal is transmitted to the nucleus to increase Bas1 and Pho2 interaction, recruiting Pho2 to promoters and freeing the activation domains for transactivation [8].
• Derepression requires the transcriptional activators Bas1 and Pho2, as well as the biosynthetic intermediates 5'-phosphoribosyl-4-succinocarboxamide-5-aminoimidazole (SAICAR) and 5'-phosphoribosyl-4-carboxamide- 5-aminoimidazole (AICAR) [8].

Physical interactions of BAS1

• These results suggest that glycine affects Bas1p activation of transcription rather than DNA binding and that Bas2p is not required for this affect [5].

Regulatory relationships of BAS1

• A Bas1p-VP16 fusion protein activated expression in a bas1bas2 strain but no glycine effect was observed while a Bas1p-Bas2p fusion protein activated expression to a lesser extent with a slight stimulation by glycine [5].

Other interactions of BAS1

• The BAS1p-BAS2p complex activates the HIS7 gene in response to adenine limitation [4].
• The hot spot activity associated with the HIS4 gene requires the Bas1p transcription factor [9].
• Interestingly, transcription of the PHO5 gene, which is dependent on Bas2p but not on Bas1p, was found to be severely impaired by oxidative stress [10].
• In wild-type and bas1 strains, meiotic recombination was strongly suppressed in large (25- to 150-kb) chromosomal regions near the telomeres and centromeres and in the region flanking the rRNA genes [9].

Analytical, diagnostic and therapeutic context of BAS1

• These data combined with LacZ fusions and northern blot analysis allow us to show that synthesis of enzymes for all 10 steps involved in purine de novo synthesis is repressed in the presence of adenine and requires BAS1 and BAS2 for optimal expression [6].
• Using indirect immunofluorescence, we found that Bas1 is localized to the nucleus under both repressing and derepressing conditions [8].
• To determine whether this relationship between transcription factor binding and hot spot activity is general, we used DNA microarrays to map all genomic Bas1p binding sites and to map the frequency of meiosis-specific double-strand DNA breaks (as an estimate of the recombination activity) of all genes in both wild-type and bas1 strains [9].
• Proteolysis protection, fluorescence quenching and circular dichroism experiments further indicated that DNA binding induces structural changes making Bas1p less accessible to modifying agents [11].

References