Related Experiment Videos
Phosphorylation of class II transactivator regulates its interaction ability and transactivation function
Tyler J Sisk1, Kevin Nickerson, Roland P S Kwok
1Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
International Immunology
|September 19, 2003
Summary
The MHC class II transactivator (CIITA) phosphorylation regulates its interactions with co-activators, controlling MHC class II gene expression. This process is crucial for adaptive immunity and requires cAMP-dependent protein kinase (PKA) activity.
Area of Science:
- Immunology
- Molecular Biology
- Gene Regulation
Background:
- The MHC class II transactivator (CIITA) is essential for adaptive immune responses.
- CIITA orchestrates MHC class II gene expression by forming enhanceosome complexes with DNA-binding and co-activator proteins.
Purpose of the Study:
- To investigate the role of CIITA phosphorylation in regulating its interactions and transactivation potential.
- To identify the kinase responsible for CIITA phosphorylation and the specific sites involved.
Main Methods:
- In vitro phosphorylation assays using cAMP-dependent protein kinase (PKA).
- Analysis of CIITA interactions with co-activators (p300, RFX5) and self-association.
- Reporter gene assays to measure MHC class II promoter activity using wild-type and mutant CIITA.
Main Results:
- Hyper-phosphorylated CIITA interacts with p300, RFX5, and itself, enhancing MHC class II promoter activity.
- The C-terminal leucine-rich repeat (LRR) domain regulates CIITA self-association, negatively impacted by phosphorylation.
- PKA phosphorylates serine residues in CIITA, and this phosphorylation is critical for maximal transactivation, as shown by reduced activity in serine mutants.
Conclusions:
- CIITA phosphorylation status dictates its protein interactions and regulatory functions.
- PKA-mediated phosphorylation of specific serine residues is essential for CIITA's role in MHC class II gene expression and adaptive immunity.