High impact information on HAP3

• Most surprisingly, the subunits of CP1 and HAP2/HAP3 are functionally interchangeable [1].
• Yeast HAP2 and HAP3 activators both bind to the CYC1 upstream activation site, UAS2, in an interdependent manner [2].
• We show here that both HAP2 and HAP3 in yeast extracts bind to UAS2UP1 and give rise to a single protein-DNA complex, termed C, in nondenaturing polyacrylamide gels [2].
• Furthermore, we demonstrate that purified recombinant HAP2, HAP3, and HAP5 are able to reconstitute CCAAT-binding activity in mobility shift analysis [3].
• Previous studies have demonstrated that the HAP2, HAP3, and HAP4 subunits of the yeast CCAAT-binding factor are required for the transcriptional activation of genes containing a CCAAT box [3].

Biological context of HAP3

• The promoter of this gene contains a number of motifs for DNA-binding transcriptional activators, including three which show strong sequence homology to the core HAP2/HAP3/HAP4 binding motif [4].
• Mutations in HAP2, HAP3 or HAP4 block derepression of a CIT1-lacZ gene fusion [5].
• Consensus sequences for the binding of yAP1 and the HAP2/HAP3/HAP4 complex are contained in those regions [6].
• Analysis of the HAP3 DNA sequence showed that the 570-base transcript could encode a protein of 144 amino acids [7].
• The predicted amino acid sequence of HapC shows extensive identity to HAP3 in the central conserved domain, but shows little conservation in the flanking sequences [8].

Anatomical context of HAP3

• Functional homologs of HAP2 and HAP3 have been conserved in HeLa cells where HAP2 activity corresponds to a chromatographic fraction designated CP1B [9].

Associations of HAP3 with chemical compounds

• In hap2, hap3 and hap4 null mutants, the specific activities of LPDH in cultures grown on galactose and raffinose showed only slight induction above the basal level on glucose medium [4].
• The hap1 mutant grew at near-normal rates on glycerol, whereas hap2 and hap3 mutants grew very slowly [10].
• We show that HEM1 (encoding 5-aminolevulinate synthase) expression, while constitutive under all steady-state growth conditions tested, is activated by the HAP2-HAP3 global activation system that controls expression of apocytochromes [11].
• The protein contains a novel 4-cysteine zinc-finger motif and we propose by analogy that all other homologous HAP3 proteins contain the same motif, with the position containing the third cysteine being occupied by a serine residue [12].

Physical interactions of HAP3

• We describe a detailed genetic analysis of the DNA-binding regions in the HAP2/HAP3 CCAAT-binding heteromeric complex [13].

Regulatory relationships of HAP3

• This HAP3 mutation also suppresses mutations in a different region of HAP2 which promotes subunit assembly of the complex [13].

Other interactions of HAP3

• Identification and characterization of HAP4: a third component of the CCAAT-bound HAP2/HAP3 heteromer [14].
• Simultaneous effects of mutations in the transcriptional regulatory genes, HAP1, HAP2 and HAP3, on all respiratory cytochromes of Saccharomyces cerevisiae were determined [10].
• Transcriptional activation by the yeast CYC1 upstream activation site UAS2UP1 requires the products of both the HAP2 and HAP3 regulatory genes [2].

Analytical, diagnostic and therapeutic context of HAP3

• Purification and molecular cloning of the "A" chain of a rat heteromeric CCAAT-binding protein. Sequence identity with the yeast HAP3 transcription factor [15].

References