Differential expression of cytosolic and mitochondrial 3-hydroxy-3-methylglutaryl CoA synthases during adipocyte differentiation.
Mitochondrial and cytosolic 3-hydroxy-3-methylglutaryl CoA synthase (m-HMS and c-HMS) genes show high identity at the nucleotide and amino acid level, but no homology has been found in the promoter area. The main regulator for c-HMS is SREBP. The best known transcription factor that regulates m-HMS is PPAR alpha. Three types of PPAR, alpha, gamma and delta have been described in vertebrates. Here we found that they display distinct ligand response profiles in the m-HMS promoter. In some conditions PPAR gamma is a significant activator of m-HMS. Thus, the m-HMS gene is transiently expressed during the clonal expansion phase of 3T3-L1 differentiation. We found that C/EBP delta and PPAR gamma activate the m-HMS promoter in 3T3-L1 cells synergistically. This synergistic effect was only observed in the whole promoter (-1148 to +28). A small construct (-116 to +28) which contains the PPRE did not respond to C/EBP delta and/or PPAR gamma. This suggests that a putative C/EBP site lie somewhere between -1148 and -116 bp. We also show that C/EBP delta was more efficient that C/EBP alpha and C/EBP beta to activate the m-HMS promoter. The time course of c-HMS mRNA expression during 3T3-L1 differentiation was different, with a significant increase at terminal adipogenesis. We found that the transcription factor C/EBP alpha did not activate the c-HMS promoter. The differential pattern of expression shown by these two genes, which have a common ancestor, exemplifies refinements of transcriptional control during evolution.
Departament de Bioquímica i Biologia Molecular, Facultat de Farmàcia, Barcelona, Spain.
J M
JM
Lopez
F G
FG
Hegardt
D
D
Haro
D017667:Adipocytes / Q000166:cytology* / Q000201:enzymology*; D000818:Animals; D015152:Blotting, Northern; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000096:biosynthesis / Q000235:genetics*; D008928:Mitochondria / Q000201:enzymology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D006904:Hydroxymethylglutaryl-CoA Synthase