ISOLATION OF THE ASPERGILLUS-NIDULANS SUDD GENE AND ITS HUMAN HOMOLOG

We have been studying the heat-sensitive bimD6 mutation of Aspergillus nidulans. At a restrictive temperature, the chromosomes of bimD6 muta nt strains fail to attach properly to the spindle microtubules, and th e mutant also displays a high rate of chromosome loss. We previously c loned the sudA gene, an extragenic suppressor of the heat-sensitive bi mD6 mutation and showed that it coded for a DA-box or SMC protein. SMC proteins have been demonstrated to function in chromosome condensatio n, segregation and global gene regulation. We have now cloned the sudD gene, another of the extragenic suppressor genes of the bimD6 mutatio n. The predicted SUDD protein is the founding member of a widely expre ssed protein family. Similar proteins are found in sequence databases for Saccharomyces cerevisiae, Caenorhabditis elegans, mammals and four species of archaebacteria. We have also cloned and sequenced a human cDNA that encodes the human homologue of SUDD and mapped the gene to 1 8q11.2. The predicted SUDD proteins from A. nidulans, Homo sapiens and S. cerevisiae all share a variety of features. The predicted proteins are approximately 60 000 Da in mass and have a serine-plus-threonine content of about 11%. The evolutionary conservation of the proteins su ggests an ancient origin and conserved function for these proteins. (C ) 1998 Elsevier Science B.V. All rights reserved.