The Structure and Expression of a Human Gene for a Nuclear-Coded Mitochondrial Adenosine Triphosphate Synthase Beta Subunit

Abstract

The beta subunit of mitochondrial ATP synthase is coded on a nuclear genome, synthesized in the cytosol, and then assembled with the other subunits which are coded on the mitochondrial genome. To determine the molecular mechanism by which the expressions on these two genetic systems are coordinated, the gene structure of the human ATP synthase beta subunit was determined, and the structure involved in this expression was analyzed. The gene for the beta subunit was found to be composed of 10 exons. The first exon corresponded to the prepiece peptide for targeting mitochondria. The 5’ upstream region contained three CAT boxes (CCAAT), three GC boxes (CCGCCC) and four repeating sequences, but no typical TATA box. To determine the regulatory structure of the upstream region, fragments of various length were fused with a chloramphenicol acetyltransferase (CAT) gene and then transfected into a cultured cell. A 300 base pairs fragment was sufficient for expressing the CAT activity, and furthermore, the longer fragment (1300 base-pairs) enhanced the expression markedly. This result suggests that the gene for the human ATP synthase beta subunit has a regulatory structure. In addition, a restriction length fragment polymorphism in the gene and an interesting pseudo-gene are reported.