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Autocatalytic proteolysis of the transcription factor-coactivator C1 (HCF): a potential role for proteolytic
1Laboratory of Viral Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Site-specific proteolysis is an important biological mechanism for the regulation of cellular processes such as gene expression, cell signaling, development, and apoptosis. In transcriptional regulation, specific proteolysis regulates the localization and activity of many regulatory factors. The C1 factor (HCF), a cellular transcription factor and coactivator, undergoes site-specific proteolytic processing at a series of unusual amino acid reiterations to generate a family of amino- and carboxyl-terminal polypeptides that remain tightly associated. Expression and purification of bacterially expressed domains of the C1 factor identifies an autocatalytic activity that is responsible for the specific cleavage of the reiterations. In addition, coexpression of the autocatalytic domain with a heterologous protein containing a target cleavage site demonstrates that the C1 protease may also function in trans.
Insights
Site-specific proteolysis regulates cellular processes. The C1 factor (HCF) uses autocatalytic activity for processing, potentially acting in trans.
Area of Science:
- Molecular biology
- Biochemistry
- Cellular regulation
Background:
- Site-specific proteolysis is crucial for regulating cellular functions, including gene expression and apoptosis.
- Proteolytic processing impacts the localization and activity of regulatory factors in transcriptional regulation.
Purpose of the Study:
- To investigate the mechanism of site-specific proteolytic processing of the C1 factor (HCF).
- To identify the enzymatic activity responsible for cleaving HCF's amino acid reiterations.
- To determine if the HCF protease can function in trans.
Main Methods:
- Expression and purification of bacterially expressed domains of the C1 factor.
- Characterization of autocatalytic activity within the C1 factor domains.
- Coexpression of the C1 autocatalytic domain with a heterologous protein containing a target cleavage site.
Main Results:
- An autocatalytic activity within the C1 factor was identified, responsible for cleaving unusual amino acid reiterations.
- Proteolytic processing of HCF generates associated amino- and carboxyl-terminal polypeptides.
- The C1 protease demonstrated potential to function in trans when coexpressed with a heterologous target protein.
Conclusions:
- The C1 factor possesses intrinsic autocatalytic activity for site-specific proteolysis.
- This proteolytic mechanism generates distinct HCF polypeptides that maintain association.
- The C1 protease may play a broader role in cellular regulation by acting on other proteins in trans.