miR-21 Gene Expression Triggered by AP-1 Is Sustained through a Double-Negative Feedback Mechanism

Shuji Fujita, Taiji Ito, Taketoshi Mizutani, Shigeru Minoguchi, Nobutake Yamamichi, Kouhei Sakurai, Hideo Iba

Research output: Contribution to journalArticle

319 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)492-504
Number of pages13
JournalJournal of Molecular Biology
Volume378
Issue number3
DOIs
Publication statusPublished - 02-05-2008

All Science Journal Classification (ASJC) codes

  • Structural Biology
  • Molecular Biology

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    Fujita, S., Ito, T., Mizutani, T., Minoguchi, S., Yamamichi, N., Sakurai, K., & Iba, H. (2008). miR-21 Gene Expression Triggered by AP-1 Is Sustained through a Double-Negative Feedback Mechanism. Journal of Molecular Biology, 378(3), 492-504. https://doi.org/10.1016/j.jmb.2008.03.015