Astrocyte-specific expression of the alpha1-antichymotrypsin and glial fibrillary acidic protein genes requires activator protein-1.
An amyloid-associated serine proteinase inhibitor (serpin), alpha(1)-antichymotrypsin (ACT), is encoded by a gene located within the distal serpin subcluster on human chromosome 14q32.1. The expression of these distal serpin genes is determined by tissue-specific chromatin structures that allow their ubiquitous expression in hepatocytes; however, their expression is limited to a single ACT gene in astrocytes. In astrocytes and glioma cells, six specific DNase I-hypersensitive sites (DHSs) were found located exclusively in the 5'-flanking region of the ACT gene. We identified two enhancers that mapped to the two DHSs at -13 kb and -11.5 kb which contain activator protein-1 (AP-1) binding sites, both of which are critical for basal astrocyte-specific expression of ACT reporters. In vivo, these elements are occupied by c-jun homodimers in unstimulated cells and c-jun/c-fos heterodimers in interleukin-1-treated cells. Moreover, functional c-jun is required for the expression of ACT in glioma cells because both transient and stable inducible overexpression of dominant-negative c-jun(TAM67) specifically abrogates basal and reduces cytokine-induced expression of ACT. Expression-associated methylation of lysine 4 of histone H3 was also lost in these cells, but the DHS distribution pattern and global histone acetylation were not changed upstream of the ACT locus. Interestingly, functional AP-1 is also indispensable for the expression of glial fibrillary acidic protein (GFAP), which is an astrocyte-specific marker. We propose that AP-1 is a key transcription factor that, in part, controls astrocyte-specific expression of genes including the ACT and GFAP genes.
Gopalan
Sunita M
SM
Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA.
Wilczynska
Katarzyna M
KM
Konik
Barbara S
BS
Bryan
Lauren
L
Kordula
Tomasz
T
D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry; D047369:Chromatin Immunoprecipitation; D003850:Deoxyribonuclease I / Q000737:chemistry; D019281:Dimerization; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D005799:Genes, Dominant; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis*; D005910:Glioma / Q000473:pathology; D022781:Hepatocytes / Q000166:cytology; D006657:Histones / Q000737:chemistry; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000096:biosynthesis*; D014158:Transcription, Genetic; D014162:Transfection; D000514:alpha 1-Antichymotrypsin / Q000737:chemistry / Q000494:pharmacology*
D002843:Chromatin; D005904:Glial Fibrillary Acidic Protein; D006657:Histones; D007375:Interleukin-1; D009841:Oligonucleotides; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D000514:alpha 1-Antichymotrypsin; D012313:RNA; D003850:Deoxyribonuclease I