Astrocyte-specific Expression of the 1-Antichymotrypsin and Glial Fibrillary Acidic Protein Genes Requires Activator Protein-1

Gopalan SM, Wilczynska KM, Konik BS, Bryan L and Kordula T
Source: J Biol Chem
Publication Date: (2006)
Issue: 281(4): 1956-1963
Research Area:
Cells used in publication:
Species: human
Tissue Origin:
Nucleofector® I/II/2b
Nucleofected U373 cells with plasmid expressing dominant-negative form of c-jun (c-junTAM67) and observed that expression of GFAP and ACT was drastically reduced (compared with cells nucleofected with pUC19 control).
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.