title: A molecular map of the chicken major histocompatibility complex: the class II beta genes are closely linked to the class I genes and the nucleolar organizer.
abstract: We have cloned in a cosmid vector four DNA clusters covering 320 kb of the chicken MHC (B complex), including five class II (B-L) beta genes defining two related isotypic families. Additional B complex genes have been revealed using tissue-specific cDNA probes. A cosmid fragment has been used to isolate a cDNA for a class I (B-F) transcript. This transcript, that is by far the most divergent known member of the class I gene family, hybridized to six B-F genes present in the cosmids. One of the clusters was shown to contain two rRNA transcriptional units from the nucleolar organizer region (NOR), marking the telomeric boundary of the B complex. None of the other B complex genes hybridizes to, or has the transcriptional characteristics of mammalian MHC class II alpha or class III genes. The map we have obtained shows that the B complex does not contain well defined class I and class II regions since B-F and B-L beta genes are closely associated with unrelated genes. Moreover, class II beta genes are very closely linked to class I genes in two clusters, and to the NOR in a third one.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002645:Chickens; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003360:Cosmids; D004247:DNA / Q000235:genetics; D015342:DNA Probes; D005091:Exons; D005805:Genes, MHC Class I; D005802:Genes, MHC Class II; D008285:Major Histocompatibility Complex; D008969:Molecular Sequence Data; D005810:Multigene Family; D009693:Nucleic Acid Hybridization; D014158:Transcription, Genetic
chemical_list: D015342:DNA Probes; D004247:DNA