mRNA encoding the beta-subunit of the mitochondrial F1-ATPase complex is a localized mRNA in rat hepatocytes.
Subcellular mRNA localization has emerged as a mechanism for regulation of gene expression and protein-sorting pathways. Here we describe the different cytoplasmic presentation in rat hepatocytes of two nuclear mRNA species encoding subunits alpha and beta of the mitochondrial F1-ATPase complex. alpha-F1-ATPase mRNA is dispersed and scattered in the cytoplasm. In contrast, beta-F1-ATPase mRNA appears in rounded electron-dense clusters, often in close proximity to mitochondria. Hybridization experiments with beta2-microglobulin and beta-actin cDNA species reveal an expected subcellular distribution pattern of the mRNA species and a non-clustered appearance. Development does not alter the presentation of beta-F1-ATPase mRNA hybrids, although it affects the relative abundance of beta-F1-ATPase mRNA clusters in the cytoplasm of the hepatocyte. These findings illustrate in vivo the existence of two different sorting pathways for the nuclear-encoded mRNA species of mitochondrial proteins. High-resolution immunocytochemistry and immunoprecipitation experiments allowed the identification of the beta-subunit precursor in the cytoplasm of the hepatocyte, also suggesting a post-translational import pathway for this precursor protein. It is suggested that the localization of beta-F1-ATPase mRNA in a subcellular structure of the hepatocyte might have implications for the control of gene expression at post-transcriptional levels during mitochondrial biogenesis in mammals.
Egea
G
G
Departamento de Biologia Molecular, Universidad Autonoma de Madrid, Spain.
Izquierdo
J M
JM
Ricart
J
J
San Martín
C
C
Cuezva
J M
JM
D000818:Animals; D000831:Animals, Newborn; D002451:Cell Compartmentation; D003593:Cytoplasm / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008099:Liver / Q000166:cytology / Q000502:physiology*; D008297:Male; D008930:Mitochondria, Liver / Q000235:genetics; D011487:Protein Conformation; D011498:Protein Precursors / Q000302:isolation & purification; D006180:Proton-Translocating ATPases / Q000235:genetics* / Q000302:isolation & purification; D012333:RNA, Messenger / Q000302:isolation & purification* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar
D011498:Protein Precursors; D012333:RNA, Messenger; D006180:Proton-Translocating ATPases