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Title of article :
miR-21 Gene Expression Triggered by AP-1 Is Sustained through a Double-Negative Feedback Mechanism
Author/Authors :
Shuji Fujita، نويسنده , , Taiji Ito، نويسنده , , Taketoshi Mizutani، نويسنده , , Shigeru Minoguchi، نويسنده , , Nobutake Yamamichi، نويسنده , , Kouhei Sakurai، نويسنده , , Hideo Iba، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2008
Pages :
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Abstract :
miR-21 has been reported to be highly expressed in various cancers and to be inducible in a human promyelocytic cell line, HL-60, after phorbol 12-myristate 13-acetate (PMA) treatment. To examine molecular mechanisms involved in miR-21 expression, we analyzed the structure of the miR-21 gene by determining its promoter and primary transcripts. We show that activation protein 1 (AP-1) activates the miR-21 transcription in conjugation with the SWI/SNF complex, after PMA stimulation, through the conserved AP-1 and PU.1 binding sites in the promoter identified here. The previous findings of enhanced miR-21 expression in several cancers may therefore reflect the elevated AP-1 activity in these carcinomas. A single precursor RNA containing miR-21 was transcribed just downstream from the TATA box in this promoter, which is located in an intron of a coding gene, TMEM49. More important, expression of this overlapping gene is completely PMA-independent and all its transcripts are polyadenylated before reaching the miR-21 hairpin embedding region, indicating that miRNAs could have their own promoter even if overlapped with other genes. By available algorithms that predict miRNA target using a conservation of sequence complementary to the miRNA seed sequence, we next predicted and confirmed that the NFIB mRNA is a target of miR-21. NFIB protein usually binds the miR-21 promoter in HL-60 cells as a negative regulator and is swept off from the miR-21 promoter during PMA-induced macrophage differentiation of HL-60. The translational repression of NFIB mRNA by miR-21 accelerates clearance of NFIB in parallel with the simultaneous miR-21-independent transcriptional repression of NFIB after PMA stimulation. Since exogenous miR-21 expression moderately induced endogenous miR-21, an evolutionarily conserved double-negative feedback regulation would be operating as a mechanism to sustain miR-21 expression.
Keywords :
AP-1 , miR-21 , NFIB , miRNA , Promoter
Journal title :
Journal of Molecular Biology
Link To Document :