The class I major histocompatibility antigen gene activated in a line of SV40-transformed mouse cells is H–2D^d, not Qa/Tla

Abstract

We have previously described several complementary DNA clones isolated because they correspond to messenger RNAs present at higher levels in the simian virus 40 (SV40)-transformed BALB/c 3T3 cell line SV3T3 Cl38 than in the normal, parental BALB/c 3T3 line¹. One of these clones, pAG64, hybridizes to RNAs which, while present in BALB/c 3T3 cells, are 10–20-fold more abundant in SV3T3 Cl38 and are found at high levels in a wide variety of transformed cell lines^1,2. Nucleotide sequence analysis showed that pAG64 encodes a class I antigen of the major histocompatibility complex². To ascertain the identity of pAG64, we compared its sequence with the available sequences of d haplotype class I antigen genes [K locus³, L locus⁴, D locus⁵ and the Qa gene defined by genomic clone 27.1 (ref. 6)] and found that it showed multiple clustered differences from each of these sequences². We therefore concluded that it was not derived from the H–2K^d, H–2L^d or H–2D^d genes and thus must correspond to one of the other class I antigen genes, namely those of the Qa/Tla complex², although it was clearly not the Qa gene defined by the genomic clone 27.1. We now report subsequent findings which indicate that pAG64 in fact corresponds to the H–2D^d gene and not to a Qa/Tla gene.