Molecular organization of the class I genes of human major histocompatibility complex.

In this brief review, our main emphasis has been on the analysis of the sequence diversity among various class I genes and their functional implications. The availability of complete nucleotide sequences of 7 different genes representing different loci allowed us to derive a consensus sequence. One mouse MHC Class I gene was included in these comparisons as a representative of H2 genes Evolutionary patterns can be seen on the basis of divergence of various genes from the derived consensus sequence. At least 1 human gene which has a promoter similar to that of H2 genes and which contains a single initiation codon following this promoter (unlike all other human genes and like all the H2 genes) has been identified. Both variable and homology regions can be identified in the entire length of the gene. While exons show relatively strong conservation of sequences, the introns have many variable regions, introns 6 and 7 being the most heterogeneous. Stretches of conserved nucleotide sequences are noticed at the 3' regions of most introns. Estimation of total number of class I genes is presented on the basis of cloning experiments, and the abundance of 1 particular pseudogene is discussed.