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Effect of poly(ADP-ribose) synthetase on the expression of major histocompatibility complex (MHC) class II genes
T Taniguchi1, K Ota, Z Qu
1Medical Research Laboratory, Kochi Medical School, Japan.
Abstract:
We have studied the effect of poly(ADP-ribose) synthetase on the interferon-gamma (IFN-gamma)-inducible expression of major histocompatibility complex (MHC) class II molecules. We constructed an expression plasmid capable of expressing either a sense RNA (MT-ARS) or an antisense RNA (pAS-FL or pAS-5') for poly(ADP-ribose) synthetase. We transfected the plasmid into mouse or human macrophage tumor cells and examined the effect on the expression of MHC class II molecules. The IFN-gamma-inducible expression of MHC class II gene was considerably reduced in transformant clones (A-2, B-2), in which the synthetase was highly expressed, whereas the depletion of the synthetase due to the expression of antisense RNA for the synthetase amplified the expression of MHC class II molecules. The results indicate that the level of the synthetase critically regulates the IFN-gamma-inducible MHC class II molecules. Next, we analyzed DNase I hypersensitive sites (DHS) of mouse MHC class II, I-A beta gene and found two sites, one in the promoter region and the other one in the first intron. The DHS in first intron was less sensitive towards DNase I attack in transformant clones (A-2, B-2) in which the synthetase was synthesized in a large quantity. Thus we constructed two beta-galactosidase reporter genes, one (A beta 2.0kb-lac z) containing the promoter region to a part of the second exon of the class II gene, and the other (A beta pro-lac z) containing the promoter region of the class II gene alone. The expression of the reporter gene was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) and found that the expression of A beta 2.0kb-lac z was suppressed in the transformant clones (A-2, B-2) relevant to control cells but the expression of A beta pro-lac z was the same level among those cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Poly(ADP-ribose) synthetase levels critically regulate major histocompatibility complex (MHC) class II molecule expression. High synthetase reduces MHC class II expression, while depletion amplifies it, impacting immune responses.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- Major histocompatibility complex (MHC) class II molecules are crucial for immune responses.
- Interferon-gamma (IFN-gamma) induces MHC class II expression.
- The role of poly(ADP-ribose) synthetase in this process was unclear.
Purpose of the Study:
- To investigate the effect of poly(ADP-ribose) synthetase on IFN-gamma-inducible MHC class II expression.
- To determine how synthetase levels regulate MHC class II gene expression at a molecular level.
Main Methods:
- Constructed expression plasmids for sense and antisense poly(ADP-ribose) synthetase RNA.
- Transfected plasmids into macrophage tumor cells.
- Analyzed MHC class II expression, DNase I hypersensitive sites, and reporter gene activity (RT-PCR).
Main Results:
- High synthetase expression reduced IFN-gamma-inducible MHC class II expression.
- Antisense RNA (depleting synthetase) amplified MHC class II expression.
- Synthetase affected DNase I hypersensitivity in the MHC class II I-A beta gene's first intron, impacting promoter-proximal gene expression.
Conclusions:
- Poly(ADP-ribose) synthetase levels critically regulate IFN-gamma-inducible MHC class II molecule expression.
- The synthetase influences MHC class II gene accessibility and expression.
- Findings provide insights into immune regulation mechanisms.