Screening human EST database for identification of candidate genes in respiratory chain deficiency

Disorders of mitochondrial oxidative phosphorylation (OXPHOS) are now recognized as major causes of human metabolic diseases and several mutations of mitochondrial and nuclear genes encoding respiratory chain components have been reported. Interestingly, mutations of nuclear genes involved in mitochondrial respiratory chain assembly, protein trafficking, and iron metabolism are also known to alter oxidative phosphorylation. While several hundred of these genes have been described in yeast, only a few nuclear genes have been hitherto identified in humans. Yeast gene databases present therefore an invaluable tool for identification of human homologues that should be regarded as candidate genes in OXPHOS diseases. In an attempt to identify the human counterparts of yeast genes, we developed a systematic comparison of yeast protein sequences to the GenBank dbEST database. Starting from 340 yeast protein sequences as templates, we searched the human dbEST counterparts using the BLAST similarity searching program and identified 102 groups of human EST likely to represent orthologues of yeast genes because of significant homology. This collection of human genes possibly related to mitochondrial OXPHOS may help identify nuclear genes responsible of mitochondrial disorders.