| Summary: | 碩士 === 國立臺灣大學 === 免疫學研究所 === 93 === After engagement of the TCR by the appropriate peptide-MHC complex, Helper T (Th) cells differentiate into Th1 or Th2 cells, which specialize in producing distinct cytokines to mediate different types of immune responses.
c-Maf, a basic region/leucine zipper transcription factor, is induced during normal T cell differentiation along a Th2 but not Th1 lineage. In Th2 cells, c-Maf directs the production of IL-4 but not other Th2 cytokines; in macrophage, c-Maf selectively inhibits transcriptional activation of IL-12 p40 and p35 genes while potently activating IL-10 and IL-4 expression. These phenomena suggest that c-Maf displays different roles in different cell types, perhaps through interacting with distinct cell-specific proteins.
For finding out the possible interacting partners, yeast-two-hybrid system was performed by using a 138bp c-Maf as the bait, and the activated Th library as the prey. Finally, PIAS1 and UBC9 were identified.
PIAS1 and UBC9 both participate in the process of sumoylation as the E2-conjugating enzyme and E3-ligase, respectively. Sumoylation is a post-translational modification that modifies many proteins.
In these studies, I demonstrated the in vivo interaction between PIAS1, UBC9, and c-Maf by co-immunoprecipitation. The functional analysis of sumoylated c-Maf was also performed by luciferase assay. The data show that sumoylation of c-Maf reduced the transactivation activity on IL-4 promoter.
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