A 150-base pair 5' region of the MHC class I HLA-B7 gene is sufficient to direct tissue-specific expression and locus control region activity: the alpha site determines efficient expression and in vivo occupancy at multiple cis-active sites throughout this region.
To characterize cis- and trans-acting mechanisms that regulate MHC class I transcription during development and in adult tissues, we have used transgenic mice to study a series of human MHC (HLA)-B7 class I gene constructs. Previous studies identified the 5' -0.66-kb to -0.075-kb region as sufficient to direct appropriate and efficient tissue-specific levels of HLA-B7 RNA relative to H-2 class I. Results here show that DNA 5' of -0.26 kb is not required for any aspect of expression. As the expression level correlated with the transgene copy number, was comparable to H-2 or a per-gene copy basis and was independent of integration site, the -0.075 to -0.26-kb segment also functions as a locus control region. With this region, sequences 3' of -0.075 kb, possibly at the promoter, appear to direct the appropriate tissue distribution. Of conserved sequences in the -0.075 to -0.26-kb region, enhancer B box is nonessential. In contrast, in vivo "footprinting" implicated region I/ enhancer A/NF-kappaB, IFN consensus/response sequence, and alpha in class I regulation as they are "occupied" in a tissue-specific pattern that correlates with expression. Mutation of alpha leads to decreased expression and loss of occupancy not only at alpha but also at region I/enhancer A/NF-kappaB and IFN consensus/response sequence. Thus, site alpha is an essential class I regulatory element, the dominant function of which is to mediate tissue-specific occupancy at multiple adjacent cis-active sites, possibly by facilitating stable synergistic interactions between factors at these distinct elements.
Kushida
M M
MM
Research Institute, The Hospital for Sick Children, University of Toronto, Ontario, Canada.
Dey
A
A
Zhang
X L
XL
Campbell
J
J
Heeney
M
M
Carlyle
J
J
Ganguly
S
S
Ozato
K
K
Vasavada
H
H
Chamberlain
J W
JW
D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D017124:Conserved Sequence / Q000276:immunology; D004622:Embryo, Mammalian; D047108:Embryonic Development / Q000276:immunology; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology*; D005805:Genes, MHC Class I; D015793:HLA-B7 Antigen / Q000235:genetics*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics / Q000276:immunology; D011247:Pregnancy; D019076:Transgenes / Q000276:immunology
D015793:HLA-B7 Antigen