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Regulation of the TRAP Promoter by IL‐4
Author(s) -
Yu Minjun,
Moreno Jose L.,
Stains Joseph P.,
Keegan Achsah D.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1070.3
Subject(s) - chromatin immunoprecipitation , microbiology and biotechnology , chemistry , stat6 , promoter , transcription (linguistics) , transcription factor , downregulation and upregulation , tartrate resistant acid phosphatase , luciferase , stat1 , transfection , rankl , biology , osteoclast , gene expression , gene , activator (genetics) , biochemistry , receptor , linguistics , philosophy
IL‐4 inhibits RANKL‐induced osteoclast formation, functional activity, and expression of tartrate‐resistant acid phosphatase (TRAP), a key osteoclast marker, in a STAT6‐dependent manner. Since the TRAP promoter contains a STAT6‐binding motif, we proposed that STAT6 directly regulates TRAP transcription. To test this, RAW264.7 cells were transfected with a TRAP promoter‐luciferase reporter. IL‐4 suppressed the ability of RANKL to upregulate TRAP‐luc activity after 72 hours, suggesting that IL‐4 represses RANKL‐induced transcription of the TRAP promoter. Similarly, we found that IL‐4 reduced the association of RNA polymerase II with the TRAP gene by chromatin immunoprecipitation (ChIP). Further, we found that STAT6 binds to the endogenous TRAP promoter within the first 24 hours of IL‐4 treatment; this binding was not observed at later times. To determine the impact of this STAT6 binding, we transfected cells with STAT6VT, an active STAT6 mutant. STAT6VT alone slightly upregulated TRAP‐luc activity, and did not inhibit the upregulation of TRAP promoter activity caused by NFATc1, PU.1 and MITF overexpression C downstream targets of M‐CSF and RANKL. These results suggest that STAT6 binds the TRAP promoter transiently after IL‐4 treatment enhancing transcription. However, STAT6 binding may not be directly responsible for the suppression of RANKL‐induced TRAP promoter activity by IL‐4.