ATRA activates and PDGF-BB represses the SM22α promoter through KLF4 binding to, or dissociating from, its cis-DNA elements.
OBJECTIVE
Krüppel-like factor 4 (KLF4) is implicated in all-trans retinoic acid (ATRA)-induced and platelet-derived growth factor-BB (PDGF-BB)-repressed SM22α expression in vascular smooth muscle cells (VSMCs). However, its exact mechanism of action remains unclear. We determined how KLF4 plays different roles in ATRA- and PDGF-BB-dependent regulation of the SM22α gene.


RESULTS
ATRA and PDGF-BB induced KLF4 expression but exhibited an opposite effect on SM22α expression and VSMC proliferation. Chromatin immunoprecipitation and oligonucleotide pull-down assays showed that KLF4 was directly bound to the KLF4 binding sites 1 ((-263)CACCC(-259)) and 2 ((-136)GTGGG(-132)) of the SM22α promoter. ATRA increased the binding of KLF4 to site 2, whereas PDGF-BB decreased the binding of KLF4 to site 1. ATRA stimulated KLF4 acetylation by inducing KLF4 phosphorylation and increasing its interaction with p300 via activating c-Jun NH(2)-terminal kinase (JNK) and p38 pathways, and acetylated KLF4 increased its binding activity to site 2. PDGF-BB stimulated KLF4 deacetylation by inducing KLF4 dephosphorylation and increasing its interaction with histone deacetylase 2 (HDAC2) via activating extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathways, and deacetylated KLF4 dissociated from site 1.


CONCLUSIONS
In VSMCs, ATRA activates and PDGF-BB represses SM22α expression through KLF4 binding to, or dissociating from, its different cis-elements in an acetylation-dependent manner.
Key Laboratory of Neural and Vascular Biology, Department of Biochemistry and Molecular Biology, Ministry of Education, Hebei Medical University, No. 361, Zhongshan East Road, Shijiazhuang 050017, China.
Kun
K
Yu
Bin
B
Zheng
Mei
M
Han
Jin-kun
JK
Wen
D000107:Acetylation; D000818:Animals; D001483:Base Sequence; D000077214:Becaplermin; D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D055785:Gene Knockdown Techniques; D056464:Histone Deacetylase 2 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008840:Microfilament Proteins / Q000235:genetics*; D009124:Muscle Proteins / Q000235:genetics*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D020574:Proto-Oncogene Proteins c-sis; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
C000715469:Klf4 protein, rat; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D008840:Microfilament Proteins; D009124:Muscle Proteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D034741:RNA, Small Interfering; C051615:transgelin; D000077214:Becaplermin; D014212:Tretinoin; D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C533426:Hdac2 protein, rat; D056464:Histone Deacetylase 2