Transcriptional regulation of CD4 gene expression by T cell factor-1/beta-catenin pathway.
By interacting with MHC class II molecules, CD4 facilitates lineage development as well as activation of Th cells. Expression of physiological levels of CD4 requires a proximal CD4 enhancer to stimulate basic CD4 promoter activity. T cell factor (TCF)-1/beta-catenin pathway has previously been shown to regulate thymocyte survival via up-regulating antiapoptotic molecule Bcl-xL. By both loss and gain of function studies, in this study we show additional function of TCF-1/beta-catenin pathway in the regulation of CD4 expression in vivo. Mice deficient in TCF-1 displayed significantly reduced protein and mRNA levels of CD4 in CD4+ CD8+ double-positive (DP) thymocytes. A transgene encoding Bcl-2 restored survival but not CD4 levels of TCF-1(-/-) DP cells. Thus, TCF-1-regulated survival and CD4 expression are two separate events. In contrast, CD4 levels were restored on DP TCF-1(-/-) cells by transgenic expression of a wild-type TCF-1, but not a truncated TCF-1 that lacks a domain required for interacting with beta-catenin. Furthermore, forced expression of a stabilized beta-catenin, a coactivator of TCF-1, resulted in up-regulation of CD4. TCF-1 or stabilized beta-catenin greatly stimulated activity of a CD4 reporter gene driven by a basic CD4 promoter and the CD4 enhancer. However, mutation of a potential TCF binding site located within the enhancer abrogated TCF-1 and beta-catenin-mediated activation of CD4 reporter. Finally, recruitment of TCF-1 to CD4 enhancer was detected in wild-type but not TCF-1 null mice by chromatin-immunoprecipitation analysis. Thus, our results demonstrated that TCF/beta-catenin pathway enhances CD4 expression in vivo by recruiting TCF-1 to stimulate CD4 enhancer activity.
Huang
Zhaofeng
Z
Department of Microbiology & Immunology, College of Medicine, University of Illinois, Chicago, IL 60612, USA.
Xie
Huimin
H
Ioannidis
Vassilio
V
Held
Werner
W
Clevers
Hans
H
Sadim
Maureen S
MS
Sun
Zuoming
Z
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015704:CD4 Antigens / Q000235:genetics*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051822:T Cell Transcription Factor 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
D015704:CD4 Antigens; D012333:RNA, Messenger; D051822:T Cell Transcription Factor 1; D051176:beta Catenin; D004247:DNA