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CIF150, a human cofactor for transcription factor IID-dependent initiator function
1Institute for Molecular Biology and Tumor Research, Philipps University, Marburg, Germany. Joerg_Kaufmann@chiron.com
Abstract:
The transcription factor IID (TFIID) complex is highly conserved between the Drosophila and mammalian systems. A mammalian homolog has been described for all the Drosophila TATA box-binding protein-associated factors (TAFs), with the exception of dTAF(II)150. We previously reported the identification of CIF, an essential cofactor for TFIID-dependent transcription from promoters containing initiator (Inr) elements. Here we describe the molecular cloning of CIF150, the human homolog of dTAF(II)150, and present biochemical evidence that this factor is involved in Inr activity. CIF150 is capable of mediating TFIID-dependent Inr activity in a complementation assay, and a protein fraction lacking Inr activity lacks detectable amounts of CIF150. Despite the striking similarity to dTAF(II)150, CIF150 does not appear to be associated with human TFIID. However, in vitro binding assays revealed a specific and direct interaction between CIF150 and hTAF(II)135. This interaction might be structurally important for the functional interaction between CIF150 and human TFIID, since CIF150 stabilizes TFIID binding to a core promoter.
Insights
Researchers identified CIF150, the human homolog of dTAF(II)150, crucial for initiator (Inr) element transcription. This protein stabilizes TFIID binding to core promoters, enhancing transcription initiation.
Area of Science:
- Molecular Biology
- Gene Regulation
- Biochemistry
Background:
- Transcription factor IID (TFIID) is vital for gene transcription and is conserved across species.
- Most Drosophila TAFs have mammalian homologs, except dTAF(II)150.
- CIF is a known cofactor for TFIID-dependent transcription at initiator (Inr) elements.
Purpose of the Study:
- To clone and characterize the human homolog of dTAF(II)150.
- To investigate the role of this human homolog in initiator (Inr) element activity.
- To elucidate the interaction of this factor with the human TFIID complex.
Main Methods:
- Molecular cloning of the human homolog of dTAF(II)150 (CIF150).
- Biochemical assays to assess Inr activity mediation.
- Complementation assays to evaluate CIF150's functional role.
- In vitro binding assays to determine protein interactions.
Main Results:
- CIF150, the human homolog of dTAF(II)150, was cloned.
- CIF150 mediates TFIID-dependent Inr activity.
- CIF150 interacts directly with hTAF(II)135.
- CIF150 stabilizes TFIID binding to core promoters, despite not being part of the canonical human TFIID complex.
Conclusions:
- CIF150 plays a significant role in initiator element-driven transcription in humans.
- CIF150's interaction with hTAF(II)135 is important for its function.
- CIF150 enhances TFIID function by stabilizing its core promoter binding.