Related Experiment Videos
Inhibitory effect of myristylation on transrepression by FBR (Gag-Fos) protein
Abstract:
The myristylated v-fos product, FBR murine sarcoma virus (Gag-Fos) protein, exhibits a lower level of transrepression of the serum response element (SRE) than does c-fos protein (Fos). Mutation of the N-terminal myristylation site in FBR protein restored SRE transrepression. Replacement of N-terminal viral Gag sequences with the Fos N terminus also restored this activity, providing additional evidence that myristylation inhibits transrepression by FBR protein. However, the myristylated Gag domain did not inhibit SRE transrepression when fused to Fos, indicating that myristylation of a fos protein is not by itself sufficient to prevent SRE transrepression and that C-terminal mutation is necessary to inhibit transrepression by N myristylation. Comparison of transfection results with Fos C-terminal deletion mutants and the Fos/FBR chimeric mutant revealed that the FBR C terminus retained the potential for transrepression despite deletion of the normal Fos C terminus, whereas similar Fos deletion mutants did not. These results indicate that both N- and C-terminal mutations are required to inhibit transrepression by FBR protein and that multiple structural mutations accompanied by posttranslational protein modification alter gene regulation by FBR protein.
Insights
Myristylation of FBR protein, a v-fos product, inhibits gene transrepression. Both N- and C-terminal mutations are necessary to alter gene regulation by FBR protein, unlike c-fos protein.
Area of Science:
- Molecular Biology
- Oncogenic Viral Proteins
- Gene Regulation
Background:
- The FBR murine sarcoma virus (FBR) Gag-Fos protein, a myristylated v-fos product, shows reduced transrepression of the serum response element (SRE) compared to c-fos (Fos).
- Understanding the structural and posttranslational modifications affecting FBR protein's transrepression activity is crucial for comprehending its role in gene regulation.
Purpose of the Study:
- To investigate the role of N-terminal myristylation and C-terminal structure in the altered transrepression activity of FBR protein.
- To determine the specific contributions of different protein domains and modifications to the inhibition of SRE transrepression.
Main Methods:
- Site-directed mutagenesis to alter the N-terminal myristylation site of FBR protein.
- Construction of chimeric proteins by replacing N-terminal sequences.
- Analysis of transrepression activity using serum response element (SRE) reporter assays.
- Comparison of transfection results with Fos C-terminal deletion mutants and Fos/FBR chimeric mutants.
Main Results:
- Mutation of the N-terminal myristylation site in FBR protein restored SRE transrepression activity.
- Replacing N-terminal Gag sequences with the Fos N terminus also restored transrepression, indicating myristylation inhibits FBR activity.
- Myristylation of Fos protein alone did not inhibit transrepression, and C-terminal mutations were also necessary.
- The FBR C terminus retained transrepression potential even after deletion of the normal Fos C terminus, unlike Fos mutants.
Conclusions:
- Both N-terminal myristylation and C-terminal structural alterations are required to inhibit transrepression by FBR protein.
- Multiple structural mutations and posttranslational modifications collectively contribute to the altered gene regulatory function of FBR protein.