Human interferon consensus sequence binding protein is a negative regulator of enhancer elements common to...

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• Interferon-inducible genes possess a shared DNA motif, the interferon consensus sequence (ICS).
• Several regulatory proteins bind to the ICS, influencing gene expression.
• A murine ICS binding protein (M-ICSBP) has been previously identified.

Purpose of the Study:

• To clone and characterize the human homologue of ICSBP (H-ICSBP).
• To investigate the DNA binding domain and regulatory function of H-ICSBP.
• To elucidate the role of H-ICSBP in interferon-inducible gene regulation in hematopoietic cells.

Main Methods:

• Cloning of the human ICSBP (H-ICSBP) cDNA.
• Sequence homology analysis comparing H-ICSBP to known interferon regulatory factors.
• Site-directed mutagenesis to identify the DNA binding domain.
• Transient transfection assays in hematopoietic and non-hematopoietic cells.

Main Results:

• H-ICSBP shares high sequence homology with M-ICSBP.
• The N-terminal 33 amino acids of H-ICSBP are crucial for ICS DNA binding.
• H-ICSBP is expressed exclusively in hematopoietic cell lines.
• H-ICSBP functions as a negative regulator of ICS-containing promoters.
• Interferon-gamma and Interferon-beta treatment can overcome H-ICSBP-mediated repression.

Conclusions:

• H-ICSBP is a novel interferon regulatory factor predominantly expressed in hematopoietic cells.
• H-ICSBP negatively regulates interferon-inducible genes by binding to the ICS.
• Interferon signaling alleviates H-ICSBP-mediated repression, enabling maximal gene transcription in response to interferons.