RESUMEN
B7-H4 is a recently identified B7 family member that negatively regulates T cell immunity by the inhibition of T cell proliferation, cytokine production, and cell cycle progression. In this study, we report that the genomic DNA of human B7-H4 is mapped on chromosome 1 comprised of six exons and five introns spanning 66 kb, of which exon 6 is used for alternative splicing to generate two different transcripts. Similar B7-H4 structure is also found in mouse genomic DNA in chromosome 3. A human B7-H4 pseudogene is identified in chromosome 20p11.1 with a single exon and two stop codons in the coding region. Immunohistochemistry analysis using B7-H4-specific mAb demonstrates that B7-H4 is not expressed on the majority of normal human tissues. In contrast, up to 85% (22 of 26) of ovarian cancer and 31% (5 of 16) of lung cancer tissues constitutively express B7-H4. Our results indicate a tight regulation of B7-H4 expression in the translational level in normal peripheral tissues and a potential role of B7-H4 in the evasion of tumor immunity.
Asunto(s)
Antígeno B7-1/biosíntesis , Antígeno B7-1/genética , Regulación hacia Abajo/inmunología , Perfilación de la Expresión Génica , Familia de Multigenes/inmunología , Análisis de Secuencia de ADN , Animales , Antígeno B7-1/química , Línea Celular Tumoral , Regulación hacia Abajo/genética , Exones/genética , Femenino , Perfilación de la Expresión Génica/métodos , Orden Génico/inmunología , Humanos , Intrones/genética , Neoplasias Pulmonares/química , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/inmunología , Ratones , Proteínas de Neoplasias/biosíntesis , Proteínas de Neoplasias/química , Proteínas de Neoplasias/genética , Especificidad de Órganos/genética , Especificidad de Órganos/inmunología , Neoplasias Ováricas/química , Neoplasias Ováricas/genética , Neoplasias Ováricas/inmunología , Análisis de Secuencia de ADN/métodos , Transcripción Genética/inmunología , Inhibidor 1 de la Activación de Células T con Dominio V-SetRESUMEN
Much of the nonrandom usage of V, D, and J genes in the Ab repertoire is due to different frequencies with which gene segments undergo V(D)J rearrangement. The recombination signal sequences flanking each segment are seldom identical with consensus sequences, and this natural variation in recombination signal sequence (RSS) accounts for some differences in rearrangement frequencies in vivo. Here, we have sequenced the RSS of 19 individual V(H)7183 genes, revealing that the majority have one of two closely related RSS. One group has a consensus heptamer, and the other has a nonconsensus heptamer. In vitro recombination substrate studies show that the RSS with the nonconsensus heptamer, which include the frequently rearranging 81X, rearrange less well than the RSS with the consensus heptamer. Although 81X differs from the other 7183-I genes at three positions in the spacer, this does not significantly increase its recombination potency in vitro. The rearrangement frequency of all members of the family was determined in microMT mice, and there was no correlation between the in vitro recombination potential and V(H) gene rearrangement frequency in vivo. Furthermore, genes with identical RSS rearrange at different frequencies in vivo. This demonstrates that other factors can override differences in RSS potency in vivo. We have also determined the gene order of all V(H)7183 genes in a bacterial artificial chromosome contig and show that most of the frequently rearranging genes are in the 3' half of the region. This suggests that chromosomal location plays an important role in nonrandom rearrangement of the V(H)7183 genes.