Induction of acute translational response genes by homocysteine. Elongation factors-1alpha, -beta, and -delta.
The thiol amino acid homocysteine (HC) accumulates in homocystinuria and homocyst(e)inemia, and is associated with a wide variety of clinical manifestations. To determine whether HC influences the cell's program of gene expression, vascular endothelial cells were treated with HC for 6-42 h and analyzed by differential display. We found a 3-7-fold, time-dependent induction of a 220-base pair fragment, which demonstrated complete sequence identity with elongation factor-1delta (EF-1delta), a member of the multimeric complex regulating mRNA translation. Fibroblasts from cystathionine beta-synthase -/- individuals also showed up to 3.0-fold increased levels of mRNA for EF-1alpha, -beta, and -delta when compared with normal cells, and treatment of normal cells with the HC precursor, methionine, induced a 1.5-2.0-fold increase in EF-1alpha, -beta, and -delta mRNA. This induction was completely inhibited by cycloheximide and reflected a doubling in the rate of gene transcription in nuclear run-on analyses. In HC-treated endothelial cells, pulse-chase studies revealed a doubling in the rate of synthesis of the thiol-containing protein, annexin II, but no change in synthesis of the cysteineless protein, plasminogen activator inhibitor-1. Thus, HC induces expression of a family of acute translational response genes through a protein synthesis-dependent transcriptional mechanism. This process may mediate accelerated synthesis of free thiol-containing proteins in response to HC-induced oxidative stress.
Divisions of Hematology-Oncology, Departments of Pediatrics and Medicine, Cornell University Medical College, New York, New York 10021, USA.
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D000595:Amino Acid Sequence; D017306:Annexin A2 / Q000378:metabolism; D001483:Base Sequence; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003541:Cystathionine beta-Synthase / Q000172:deficiency; D004730:Endothelium, Vascular / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D008715:Methionine / Q000494:pharmacology; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D018384:Oxidative Stress / Q000502:physiology; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000235:genetics*; D014176:Protein Biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics
D017306:Annexin A2; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D012333:RNA, Messenger; D013438:Sulfhydryl Compounds; D006710:Homocysteine; D003513:Cycloheximide; D008715:Methionine; D003541:Cystathionine beta-Synthase