Cloning and functional analyses of the mouse tapasin promoter.
The expression of tapasin is critical for an optimized MHC class I assembly and stable MHC class I surface expression. Thus, impaired MHC class I antigen expression of tumors can be attributable to tapasin downregulation. In order to understand the molecular mechanisms of deficient tapasin expression, the mouse tapasin promoter region and its 5'-flanking sequences were characterized. The mouse tapasin promoter lacks the TATA box and its transcription is initiated at multiple sites within a 51-nucleotide stretch. Sequence analyses revealed transcription factor binding motifs for NF-kappaB, GATA, E2F, p300, AP1, SP1 and IRF-1/2. Detailed analysis of deletion mutants and elimination of transcription factor binding motifs demonstrated an important role of NF-kappaB at position -468 for its basal activity, whereas E2F at position -229 represses constitutive promoter activity. Furthermore, the IRF-1/2 binding site is required for gamma interferon inducibility of the tapasin promoter in vitro, but also negatively interferes with its constitutive activity. Thus, characterization of the tapasin promoter represents the molecular basis for the understanding of the heterogeneous expression levels of tapasin under physiological and pathophysiological conditions.
Herrmann
Felix
F
3rd Department of Internal Medicine, Johannes Gutenberg University, 55131 Mainz, Germany.
Trowsdale
John
J
Huber
Christoph
C
Seliger
Barbara
B
D000818:Animals; D017920:Antiporters / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D007136:Immunoglobulins / Q000235:genetics*; D007371:Interferon-gamma / Q000096:biosynthesis / Q000235:genetics; D026901:Membrane Transport Proteins; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D024363:Transcription Initiation Site
D017920:Antiporters; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D016328:NF-kappa B; C107762:tapasin; D007371:Interferon-gamma; D004247:DNA