Egr-1, a serum-inducible zinc finger protein, regulates transcription of the rat cardiac alpha-myosin heavy chain gene.
Egr-1 is an early growth response gene that encodes a protein with three zinc fingers and is involved in transcriptional regulation. In adult heart myocytes, in contrast to c-fos and c-myc, high levels of Egr-1 mRNA expression have been shown. Here we report that Egr-1 transactivates rat cardiac alpha-MHC gene expression. In serum-starved primary cultures of 18-day-old fetal rat heart myocytes, addition of serum evoked expression of both Egr-1 and alpha-MHC gene transcripts. Inclusion of 10 microM cycloheximide in these cultures for 48 h caused a greater increase in Egr-1 mRNA, whereas the expression of alpha-MHC transcripts was ablated. To examine the involvement of Egr-1 in alpha-MHC induction, we transfected primary cultures of cardiac myocytes with plasmids pCMVEgr-1 (Egr-1 expression vector) and pMP3.3CAT containing -2.9- to +0.42-kilobase sequences of the alpha-MHC gene fused to the coding region of the chloramphenicol acetyltransferase (CAT) gene. Cotransfection of pCMVEgr-1 stimulated expression of pMP3.3CAT 10-15-fold. Furthermore, pCMVEgr-1 also stimulated expression of the endogenous alpha-MHC gene in primary cultures of cardiac myocytes. Transactivation of pMP3.3CAT expression by pCMVEgr-1 was also observed by transfecting the myogenic cell line Sol 8, but not in L6E9 cells or in NIH3T3 fibroblasts. By creating progressive 5' deletions of the alpha-MHC gene, we found that the region extending between -1698 and -1283 base pairs is necessary for Egr-1-induced expression of the alpha-MHC/CAT construct. These results define a physiological target for the Egr-1 transcription factor and delineate a novel mechanism for regulation of the alpha-MHC gene.
Gupta
M P
MP
Department of Medicine, University of Chicago, Illinois 60637.
Gupta
M
M
Zak
R
R
Sukhatme
V P
VP
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D002872:Chromosome Deletion; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D005333:Fetus; D005786:Gene Expression Regulation; D015698:Genomic Library; D006321:Heart / Q000502:physiology*; D017874:Immediate-Early Proteins; D008969:Molecular Sequence Data; D009218:Myosins / Q000235:genetics*; D015345:Oligonucleotide Probes; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D015183:Restriction Mapping; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D014157:Transcription Factors; D009218:Myosins