Comparison of nucleotide sequences from upstream of the DQ52 gene to the S mu region of immunoglobulin heavy-chain gene loci between Suncus murinus, mouse and human.

The nucleotide sequence of a 4621 base pair fragment of DNA, from a position upstream of DSQ52 to the S mu region within immunoglobulin heavy-chain gene loci of Suncus murinus was determined. The sequence contained one D gene, three JH genes and an enhancer. Suncus murinus is an insectivore and is one of the most primitive mammals. Both primates and rodents are thought to have originated from insectivores and to have evolved separately. We also determined the nucleotide sequence of a region between human JH genes and the enhancer which has not previously been reported. Thus, the sequences of the entire region from each of the three species, Suncus murinus, human and mouse are now available. Comparison of the nucleotide sequence of this region between these three species indicated that D and JH genes, consisting of coding and signal regions, are highly conserved. Moreover, although extensive sequence homology in the region between JH and S mu was observed between mouse and human, only core portions of the enhancer region of Suncus murinus exhibited homology to those of mouse and human. Sequence conservation of JH genes in Suncus murinus, mouse and human was observed not only at the amino-acid level, but also at the nucleotide level, including the third letters of the codons. It is suggested that JH genes may play a role in the metabolism of the DNA and/or RNA.