A novel DNA binding activity is elevated in thymocytes expressing high levels of H-2Dd after radiation leukemia virus infection.
Resistance to radiation leukemia virus-induced leukemia is mediated by gene(s) in the H-2D region of the MHC; a clear correlation exists between disease resistance and increased H-2Dd expression on the thymocyte surface. We have investigated the molecular basis for this stimulation of H-2Dd class I expression. Elevated H-2 mRNA and H-2 transcription are demonstrated in the infected thymocytes as compared to normal thymocytes indicating that the elevation of H-2 surface expression is the result of transcriptional activation. Gel mobility assays performed with nuclear extracts of normal and infected thymocytes and sequences 5' of the H-2Dd gene show that specific binding occurs with both extracts; the binding differs both quantitatively and qualitatively, however. DNase I protection analysis detects a protein binding site that is protected only by extracts from infected cells. The protected region contains a sequence similar to the AP-1 consensus sequence. Gel shift competition assays and UV photo-cross-linking to an oligonucleotide containing this sequence demonstrate that specific binding of an H-2 binding factor 1 occurs and that this factor is not the AP-1 binding complex. This novel binding factor, activated in vivo, might also be involved in the normal regulation of H-2 gene expression by recognizing the highly conserved binding sequence (TGACGCG) found in the 5' flanking region of many MHC class I genes. This is the first demonstration of the parallel stimulation of a DNA binding activity and increased transcription occurring in thymocytes after infection with a leukemogenic retrovirus.
Nobunaga
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T
Department of Pathology, New York University Medical Center, NY 10016.
Brown
G D
GD
Morris
D R
DR
Meruelo
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D
D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D005805:Genes, MHC Class I; D006183:H-2 Antigens / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D007942:Leukemia, Experimental / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D016721:Radiation Leukemia Virus; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D013950:Thymus Gland / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D006183:H-2 Antigens; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D014157:Transcription Factors