Mitochondrial protein expression in Ratt and in human cells

In the present paper, we analyzed some aspects of the post-transcriptional regulation of two COX (cy-tochrome c oxidase) subunits, i.e. mitochondrion-encoded COXIII and nucleus-encoded COXIV. In particular, by T1 RNase protection assays, we found two proteins, present in mitochondrial extracts from adult rat brain and testis, able to bind COXIII mRNA. We also found cytoplasmic proteins present in testis, kidney and heart extracts that bind COXIV mRNA. Moreover, to study the expression of mitochondrial proteins in tumor cells, we quantitated COXIV and Hsp60 chaperonin abundance in two epithelial cell lines from human breast, one neoplastic (MDA-MB231) and the other immortalized and non-tumoral (HB2). The results obtained showed that COXIV amount was higher in tumor cells than in immortalized cells, while Hsp60 was more abundant in HB2 cell line.