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Regulation of the smooth muscle α‐actin promoter by Purα and Purβ
Author(s) -
Knapp Anna M,
Ramsey Jon E,
Wang ShuXia,
Godburn Karolyn E,
Strauch Arthur R,
Kelm Robert J
Publication year - 2006
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.20.5.lb47-d
Subject(s) - enhancer , repressor , transcription (linguistics) , biology , gene , transcription factor , microbiology and biotechnology , sma* , genetics , linguistics , philosophy , mathematics , combinatorics
Purα and Purβ are single‐stranded DNA‐binding proteins implicated in the control of cell growth and differentiation. The goal of this study was to determine whether Purα and Purβ function in a redundant, distinct, or collaborative manner to suppress smooth muscle α‐actin (SMA) gene expression in cell types relevant to wound repair and vascular remodeling. RNA interference‐mediated loss‐of‐function analyses revealed that while Purβ was the dominant repressor, the combined action of both Purα and Purβ was necessary to silence the full‐length mouse SMA promoter in growing fibroblasts and vascular smooth muscle cells. Conversely, gain‐of‐function studies indicated that Purα or Purβ could each independently repress core SMA enhancer activity albeit in a cell type‐dependent fashion. Biochemical analyses indicated that purified recombinant Purα and Purβ were essentially identical in terms of their binding affinity and specificity for GGN repeat‐containing cis‐elements comprising the core enhancer. However, Purα and Purβ exhibited more distinctive interaction profiles when evaluated for binding to SMA enhancer‐associated transcription factors in extracts from selected cell types. Thus, Purα and Purβ appear to repress SMA gene transcription by means of strand‐selective cis‐element binding and cell type‐dependent protein‐protein interactions. This study was supported by grants R01 HL54281 (R.J.K.), T32 HL07594 (A.M.K.), and AHA 0515620T (J.E.R.).