Identification of an H-2Kb-related molecule by molecular cloning

Based on the published amino-acid sequence of H-2Kb, we synthesized a mixture of eight 16-base long oligodeoxyribonucleotides representing all possible coding sequences for residues 51-56 (Trp-Met-Glu-Gln-Glu-Gly). The hexadecanucleotide mixture was used as a probe to screen recombinant DNA clones constructed from cytoplasmic PolyA+ RNA isolated from the murine thymoma cell line EL4(b haplotype). Of the 30 000 independent clones screened, one clone was found to hybridize with the probe. DNA sequence analysis showed that the cDNA clone was derived from a portion of an H-2Kb -related mRNA. The clone encodes a protein sequence identical with a region of H-2Kb in 42 consecutive residues (50 through 91). The sequence than diverges from the H-2Kb sequence and, after a single Glu codon, a termination codon is encountered. It is possible that this mRNA codes for a small 92 amino-acid protein with a sequence identical (except for a carboxy-terminal Glu residue) with the amino terminus of H-2Kb. It is further speculated that this mRNA is coded for by the H-2Kb gene and differs from the H-2Kb mRNA in the pattern of posttranscriptional splicing.