Identification and characterization of HAP4: a third component of the CCAAT-bound HAP2/HAP3 heteromer

Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Genes & Development (Impact Factor: 10.8). 09/1989; 3(8):1166-78. DOI: 10.1101/gad.3.8.1166
Source: PubMed


The CYC1 gene of Saccharomyces cerevisiae is positively regulated by the HAP2 and HAP3 proteins, which form a heteromeric complex that binds to a CCAAT box in the upstream activation site, UAS2, and which activate transcription in a nonfermentable carbon source. We carried out a genetic analysis to identify additional trans-acting regulatory factors exerting their effects through UAS2. We present the identification and characterization of a new locus, HAP4, which is shown to encode a subunit of the DNA-binding complex at UAS2. In the hap4 mutant, the binding of HAP2 and HAP3 (HAP2/3) is not observed in vitro. The HAP4 gene is regulated transcriptionally by a carbon source, suggesting that it encodes a regulatory subunit of the bound complex. The sequence of HAP4 shows a highly acidic region, which innactivated the protein when deleted. Replacement of this region with the activation domain of GAL4 restored activity, suggesting that it provides the principal activation domain to the bound HAP2/3/4 complex.

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    • "They are transcribed but then rapidly degraded (Scheffler et al., 1998). While the HAP2/3/4/5 DNA-binding complex is involved in the transcriptional activation of genes for respiration (Forsburg and Guarente, 1989), the RNA-binding protein Puf3p, which is not a canonical transcriptional factor, has also been implicated in the regulation of such genes (Gerber et al., 2004). Puf3p is a member of the PUF (PUmilio and FBF) family of RNA-binding proteins (Murata and Wharton, 1995; Zamore et al., 1997; Zhang et al., 1997) and has been shown to specifically bind to the 3 0 UTRs of mRNAs encoding mitochondrial proteins (Jackson et al., 2004; Olivas and Parker, 2000; Ulbricht and Olivas, 2008; Zhu et al., 2009). "
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