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Heterogeneous nuclear ribonucleoprotein K is a transcription factor
E F Michelotti1, G A Michelotti, A I Aronsohn
1Laboratory of Pathology, National Cancer Institute, National Institute of Health, Bethesda, Maryland 20892, USA.
Molecular and Cellular Biology
|May 1, 1996
Summary
Heterogeneous nuclear ribonucleoprotein K (hnRNP K) activates transcription of the c-myc gene by binding to the CT element. This protein interacts with the TATA-binding protein (TBP) and the RNA polymerase II transcription machinery.
Area of Science:
- Molecular Biology
- Gene Regulation
- Transcription Factors
Background:
- The c-myc gene promoter contains a CT element, a homopyrimidine tract that binds transcription factors Sp1 and heterogeneous nuclear ribonucleoprotein K (hnRNP K).
- hnRNP K is a protein associated with hnRNP complexes with a less characterized role in transcription.
Purpose of the Study:
- To investigate the role of hnRNP K in CT element-mediated transcription activation.
- To determine the mechanism by which hnRNP K influences transcription.
Main Methods:
- In vitro transcription assays using CT element-containing templates.
- Electrophoretic mobility shift assays (EMSAs) to study DNA binding.
- Affinity chromatography to identify interacting proteins.
- Coimmunoprecipitation assays to confirm in vivo interactions.
- In vivo reporter gene assays to assess transcriptional activity.
Main Results:
- hnRNP K binds to the pyrimidine-rich strand of the CT element and activates transcription in vitro.
- Recombinant hnRNP K enhances RNA synthesis from single-stranded CT element templates.
- hnRNP K interacts with components of the TFIID complex, including the TATA-binding protein (TBP).
- hnRNP K and TBP form a complex in vivo and in vitro.
- Overexpression of hnRNP K and TBP synergistically activates CT element-dependent transcription.
Conclusions:
- hnRNP K functions as a transcription factor that binds to the CT element.
- hnRNP K interacts with the RNA polymerase II transcription machinery, specifically TBP.
- hnRNP K plays a significant role in stimulating c-myc gene transcription.