CHANGING PATTERNS OF TRANSCRIPTIONAL AND POSTTRANSCRIPTIONAL CONTROL OF BETA-F-1-ATPASE GENE-EXPRESSION DURING MITOCHONDRIAL BIOGENESIS IN LIVER

To elucidate the mechanisms that regulate the expression of nuclear ge nes during biogenesis of mammalian mitochondria, the expression patter n of the beta-subunit of the ATP synthase gene has been characterized in rat liver between day 20 in utero and 12 weeks postnatal. The paral lelism existing between transcriptional activity of the gene and the a mount of beta-F-1-ATPase protein in liver indicates that proliferation of mitochondria is controlled at the transcriptional level. On the ot her hand, an increased stability (4-5-fold) of beta-F-1-ATPase mRNA du ring early neonataI life as well as a rapid postnatal activation of tr anslation rates affecting mitochondrial proteins appear to control mit ochondrial differentiation. Immunoelectron microscopy of the F-1-ATPas e complex during liver development revealed that the rapid postnatal i ncrease in the in vivo rate of F-1-ATPase synthesis was mostly used fo r functional differentiation of pre-existing organelles (VaIcarce, C., Navarrete, it. M., Encabo, P., Loeehes, E., Satrustegui, J., and Cuez va, J. M. (1988) J. Biol Chem. 263, 7767-7775). The findings support t hat beta-F-1-ATPase mRNA decay is developmentally regulated in liver, indicating that gene expression is also controlled at this level durin g physiological transitions that affect biogenesis of mitochondria.