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Mutant p53 forms a complex with Sp1 on HIV-LTR DNA.
A Chicas1, P Molina, J Bargonetti
1Department of Biological Sciences, Institute for Biomolecular Structure and Function, Hunter College, 695 Park Avenue, New York, New York, 10021, USA.
Biochemical and Biophysical Research Communications
|December 19, 2000
Summary
Mutant p53 (His273) interacts with Sp1 bound to DNA, activating human immunodeficiency virus (HIV) transcription. This interaction suggests mutant p53 enhances HIV replication through a DNA-driven complex.
Area of Science:
- Molecular Biology
- Virology
- Cancer Biology
Background:
- Mutant p53 proteins are frequently found in cancers and can alter cellular functions.
- Certain p53 mutants activate transcription from the human immunodeficiency virus long terminal repeat (HIV-LTR), promoting viral replication.
- The Sp1-binding sites within the HIV-LTR are crucial for this observed activation.
Purpose of the Study:
- To investigate the hypothesis that mutant p53 interacts with DNA-bound Sp1.
- To determine if this interaction leads to increased transcription from Sp1-dependent promoters.
- To elucidate the mechanism by which mutant p53 influences HIV-LTR transcription.
Main Methods:
- Utilized the MDA-MB-468 breast cancer cell line expressing endogenous mutant p53(His273).
- Employed dominant-negative inhibition using p53(Val135) to assess mutant p53's role in HIV-LTR transcription.
- Performed HIV-LTR DNA affinity chromatography to detect protein interactions.
- Assessed sequence-specific DNA binding of mutant p53 to a super consensus sequence (SCS).
Main Results:
- Mutant p53(His273) was shown to activate HIV-LTR transcription in MDA-MB-468 cells.
- HIV-LTR-directed transcription was inhibited by p53(Val135), confirming mutant p53's involvement.
- Coelution of p53(His273) and Sp1 was observed using HIV-LTR DNA affinity chromatography.
- Mutant p53(His273) demonstrated sequence-specific binding to the SCS, with Sp1 coeluting from this site.
Conclusions:
- Mutant p53(His273) directly binds to Sp1 when Sp1 is associated with DNA.
- This interaction suggests a mechanism where mutant p53 enhances transcription from Sp1-dependent promoters, including the HIV-LTR.
- Activated HIV-LTR transcription by mutant p53 likely occurs via a DNA-driven multi-protein complex involving Sp1.