Multidrug Resistance Genome Of The Puffer Fish Full-length Sequence And Sitting Next To Gene Analysis

The human MDR (multil-drug resistance) gene family is composed of two members (MDRl, MDR3) which are clustered on the chromosome band 7q21.1 and span a region of about 230 kb. A human MDRl full length cDNA probe was used to screen a pufferfish cosmid library and nine clones, which would contain the whole MDR gene family in the pufferfish genome, were finally identified. One of the cosmid clones was sequenced. Sequence analysis revealed that there would be at least three MDR homologues in the corresponding region. The biggest MDR gene is of about 10.8 kb, only approximately 1/7 to 1/12 that of the human gene, but it's transcript, approximately 3.7 kb long from exon4 to exon28, is in similar size to that of the human. It's gene organization is highly conserved, especially the 12 trans-membranous domains which have been found in the MDR gene family of many organisms. The ATP-binding motif of the gene is significantly homologous. The other two MDR homologues are similar in structures but even smaller. There are total 6.5 genes in the cosmid ,with full length of 40kb, and the average size of genes is 6kb. Our preliminary data indicate that pufferfish is an ideal model for the studies of vertebrate genomes and potential for identification of human genes because of its compactness and the conserved gene order in the (?)ame evolutional blocks.