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Transcriptional regulation of human eosinophil RNase2 by the liver‐enriched hepatocyte nuclear factor 4
Author(s) -
Wang HsiuYu,
Ho PoChun,
Lan ChungYu,
Chang Margaret DahTsyr
Publication year - 2008
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.22008
Subject(s) - microbiology and biotechnology , transcription factor , activator (genetics) , promoter , transcription (linguistics) , chromatin immunoprecipitation , hepatocyte nuclear factor 4 , biology , hepatocyte nuclear factors , gene , gene expression , biochemistry , nuclear receptor , linguistics , philosophy
Abstract Human eosinophil‐derived neurotoxin (EDN, RNase2) and eosinophil cationic protein (ECP, RNase3) sequences possess as high as 92% identity in their promoter regions. The major difference within this region is a 34‐nucleotide (34‐nt) segment appeared only in the edn promoter. In addition, six discrete segments existed in the regulatory regions of both edn and ecp . Our previous study indicated that the 34‐nt segment is responsive for higher transcription activity of edn in comparison with ecp , via binding to transcription activator Sp1. In this study, the roles of the six discrete segments in transcription regulation were investigated and the −350/−329 region ( edn R2) was shown to be involved in the regulation of edn expression. When the edn R2 segment of edn was replaced with that of ecp , a significant decrease in edn promoter activity was detected. Supershift, chromatin immunoprecipitation, and DNA affinity precipitation assays further showed that a transcription factor HNF4 bound to the edn R2 region of edn promoter in vitro. Interestingly, HNF4 overexpression resulted in the reduction of edn promoter activity in HepG2 cells, due to involvement of both edn R2 and the 34‐nt regions, and direct interaction between HNF4 and Sp1, which abolishes Sp1 binging to the 34‐nt segment. Moreover, when the Sp1 was depleted in the cell, overexpressed HNF4 enhanced edn promoter activity. Our results provide novel mechanisms for HNF4 function as an activator to regulate edn promoter activity, which account for differential transcription regulation of human eosinophil RNases. J. Cell. Biochem. 106: 317–326, 2009. © 2008 Wiley‐Liss, Inc.