Related Experiment Videos
Stat proteins play a role in tumor necrosis factor alpha gene expression
V L Chappell1, L X Le, L LaGrone
1Department of Surgery, The University of Texas Medical Branch, Galveston 77555-1173, USA.
Abstract:
Trauma produces dysfunction in immunity, which appears to be partially related to alterations in the cytokine response. Signal transducer and activator of transcription proteins (STATs) mediate activation of several cytokine genes. However, the effect of STAT proteins on tumor necrosis factor-alpha (TNFalpha) activation is not fully defined. We identified binding sites for STAT 3 and STAT 5/6 within the promoter region of TNFalpha and hypothesize that alterations in these sites would affect TNFalpha expression. The TNFalpha promoter was inserted into the luciferase reporter vector, and binding sites for STAT 3, STAT 5/6, and activator protein-1 (AP-1) were mutated using site-directed mutagenesis. Murine macrophages were transfected with the resultant plasmids, then incubated with and without lipopolysaccharide (LPS) or IFNalpha. Gene expression was measured by dual luciferase assay. Mutation of the STAT 3 binding site was associated with decreased LPS-inducible activity. Mutation of the AP-1 and STAT 5/6 consensus binding sites alone had no effect on TNFalpha expression. However, combined mutation of both STAT 5/6 and AP-1 was associated with increased LPS-inducible activity. Mutations of the STAT binding sites in the promoter region of TNFalpha affect TNFalpha gene expression. These results suggest a regulatory role for STATs in TNF gene transcription.
Insights
Signal transducer and activator of transcription (STAT) proteins regulate tumor necrosis factor-alpha (TNFalpha) gene expression. STAT 3 binding site mutations decreased TNFalpha activity, suggesting a key role in immune response regulation.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Trauma-induced immune dysfunction is linked to altered cytokine responses.
- Signal transducer and activator of transcription (STAT) proteins are crucial for cytokine gene activation.
- The specific role of STAT proteins in tumor necrosis factor-alpha (TNFalpha) gene regulation remains unclear.
Purpose of the Study:
- To investigate the role of STAT 3 and STAT 5/6 binding sites in the promoter region of the TNFalpha gene.
- To determine how mutations in these STAT binding sites affect TNFalpha expression.
Main Methods:
- Site-directed mutagenesis was used to alter STAT 3, STAT 5/6, and activator protein-1 (AP-1) binding sites in the TNFalpha promoter.
- The modified TNFalpha promoter was inserted into a luciferase reporter vector.
- Murine macrophages were transfected and treated with lipopolysaccharide (LPS) or IFNalpha, with gene expression measured via dual luciferase assay.
Main Results:
- Mutation of the STAT 3 binding site significantly decreased lipopolysaccharide (LPS)-inducible TNFalpha activity.
- Individual mutations in AP-1 and STAT 5/6 binding sites did not affect TNFalpha expression.
- Combined mutation of STAT 5/6 and AP-1 binding sites led to increased LPS-inducible TNFalpha activity.
Conclusions:
- STAT binding sites within the TNFalpha promoter play a regulatory role in TNFalpha gene transcription.
- STAT 3 appears to be a key regulator of LPS-induced TNFalpha expression.
- STAT 5/6 and AP-1 may have a cooperative or opposing regulatory function in TNFalpha expression.