Developmental and tissue-specific expression of nuclear proteins that bind the regulatory element of the major histocompatibility complex class I gene.
Expression of MHC class I genes varies according to developmental stage and type of tissues. To study the basis of class I gene regulation in tissues in vivo, we examined binding of nuclear proteins to the conserved cis sequence of the murine H-2 gene, class I regulatory element (CRE), which contains two independent factor-binding sites, region I and region II. In gel mobility shift analyses we found that extracts from adult tissues that express class I genes, such as spleen and liver, had binding activity to region I. In contrast, extracts from brain, which does not express class I genes, did not show region I binding activity. In addition, fetal tissues that express class I gene at very low levels, also did not reveal region I binding activity. Binding activity to region I became detectable during the neonatal period when class I gene expression sharply increases. Most of these tissues showed binding activity to region II, irrespective of class I gene expression. Although region II contained a sequence similar to the AP-1 recognition site, AP-1 was not responsible for the region II binding activity detected in this work. These results illustrate a correlation between region I binding activity and developmental and tissue-specific expression of MHC class I genes. The CRE exerts an enhancer-like activity in cultured fibroblasts. We evaluated the significance of each factor binding to CRE. Single 2-bp mutations were introduced into the CRE by site-directed mutagenesis and the ability of each mutant to elicit the enhancer activity was tested in transient CAT assays. A mutation that eliminated region I protein binding greatly impaired enhancer activity. A mutation that eliminated region II binding also caused a lesser but measurable effect. We conclude that region I and region II are both capable of enhancing transcription of the class I gene. These results indicate that in vivo regulation of MHC class I gene expression is mediated by binding of trans-acting factors to the CRE.
Burke
P A
PA
Laboratory of Developmental and Molecular Immunity, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Hirschfeld
S
S
Shirayoshi
Y
Y
Kasik
J W
JW
Hamada
K
K
Appella
E
E
Ozato
K
K
D000818:Animals; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006183:H-2 Antigens / Q000235:genetics*; D051379:Mice; D009687:Nuclear Proteins / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid; D014018:Tissue Distribution; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D006183:H-2 Antigens; D009687:Nuclear Proteins; D014157:Transcription Factors