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Yeast HAP2 and HAP3: transcriptional activators in a heteromeric complex
1Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Science (New York, N.Y.)
|April 15, 1988
Summary
The yeast HAP2 and HAP3 proteins form a complex before binding to DNA. This complex regulates the transcription of the iso-1-cytochrome c gene via the UAS2 activation site.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Protein-DNA Interactions
Background:
- Gene transcription regulation is crucial for cellular function.
- The yeast CYC1 gene (iso-1-cytochrome c) is a key component of the respiratory chain.
- Its transcription is controlled by upstream activation sites (UAS) like UAS2.
Purpose of the Study:
- To determine if HAP2 and HAP3 activators bind DNA cooperatively or form a pre-assembled complex.
- To elucidate the mechanism of UAS2-mediated transcriptional activation.
Main Methods:
- Gene fusion of HAP2 to LexA and HAP3 to beta-galactosidase.
- Purification of tagged proteins using multiple chromatographic steps.
- Assessing UAS2 binding activity of purified protein complexes.
Main Results:
- LexA-HAP2 and HAP3-beta-galactosidase were successfully purified.
- The purified proteins retained UAS2 binding activity.
- Copurification demonstrated that HAP2 and HAP3 associate in the absence of DNA.
Conclusions:
- HAP2 and HAP3 form a stable multisubunit complex prior to DNA binding.
- This pre-formed complex is essential for regulating yeast CYC1 gene transcription at UAS2.