Nuclear factor-1-X regulates astrocyte-specific expression of the alpha1-antichymotrypsin and glial fibrillary acidic protein genes.
Discrete tissue-specific changes in chromatin structure of the distal serpin subcluster on human chromosome 14q32.1 allow a single gene encoding alpha1-antichymotrypsin (ACT) to be expressed in astrocytes and glioma cells. This astrocyte-specific regulation involves activatory protein-1 (AP-1) because overexpression of dominant-negative c-jun(TAM67) abolishes ACT expression in glioma cells. Here we identify a new regulatory element, located within the -13-kb enhancer of the ACT gene, that binds nuclear factor-1 (NFI) and is indispensable for the full basal transcriptional activity of the ACT gene. Furthermore, down-regulation of NFI expression by siRNA abolishes basal ACT expression in glioma cells. However, NFI does not mediate astrocyte-specific expression by itself, but likely cooperates with AP-1. A detailed analysis of the 14-kb long 5'-flanking region of the ACT gene indicated the presence of adjacent NFI and AP-1 elements that colocalized with DNase I-hypersensitive sites found in astrocytes and glioma cells. Interestingly, knock-down of NFI expression also specifically abrogates the expression of glial acidic fibrillary protein (GFAP), which is an astrocyte-specific marker protein. Mutations introduced into putative NFI and AP-1 elements within the 5'-flanking region of the GFAP gene also diminished basal expression of the reporter. In addition, we found, using isoform-specific siRNAs, that NFI-X regulates the astrocyte-specific expression of ACT and GFAP. We propose that NFI-X cooperates with AP-1 by an unknown mechanism in astrocytes, which results in the expression of a subset of astrocyte-specific genes.
Gopalan
Sunita M
SM
Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298.
Wilczynska
Katarzyna M
KM
Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298.
Konik
Barbara S
BS
Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298.
Bryan
Lauren
L
Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298.
Kordula
Tomasz
T
Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298. Electronic address: tkordula@vcu.edu.
D001253:Astrocytes / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051839:NFI Transcription Factors / Q000378:metabolism*; D011485:Protein Binding; D034622:RNA Interference; D018808:Transcription Factor AP-1 / Q000378:metabolism; D000514:alpha 1-Antichymotrypsin / Q000235:genetics / Q000378:metabolism*
D005904:Glial Fibrillary Acidic Protein; D051839:NFI Transcription Factors; D018808:Transcription Factor AP-1; D000514:alpha 1-Antichymotrypsin