Structural analysis of TL genes of the mouse
Genes, MHC Class II
Three Tla region-specific probes have been generated from the BALB/c genomic cosmid clone C6.3. One probe, pTL1, corresponds to 3' sequences of a thymus leukemia (TL)-encoding gene, whereas pTL2 and pTL3 detect noncoding flanking sequences. The TL specificity of pTL1 was demonstrated by studies of RNA from thymocytes of TL+ and TL- mouse strains and from TL+ and TL- leukemias; presence/absence of pTL1+ transcripts correlated with presence/absence of TL antigens detected serologically. Nine Tla haplotypes were defined by restriction fragment polymorphism with pTL1, and the number of TL genes has been estimated to be greater than or equal to 4 in Tlaa, Tlac and Tlae mice, greater than or equal to 3 in Tlad mice, and greater than or equal to 2 in Tlab and Tlaf mice. A TL-encoding gene (C25.1) from the C57BL/6TL+ leukemia ERLD has been cloned and sequenced, and the exon/intron organization of C25.1 has been deduced from the structure of pTL1+ cDNA clones and from the known organization of H-2 genes. The major structural differences between TL and H-2 genes are in exons coding for the cytoplasmic domain.