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

@article{citeulike:2644067, 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.}, author = {Fujita, Shuji and Ito, Taiji and Mizutani, Taketoshi and Minoguchi, Shigeru and Yamamichi, Nobutake and Sakurai, Kouhei and Iba, Hideo }, citeulike-article-id = {2644067}, doi = {10.1016/j.jmb.2008.03.015}, journal = {Journal of Molecular Biology}, keywords = {ap-1, function, mir-21, mirna, nfkappab}, posted-at = {2008-04-09 10:14:44}, priority = {2}, title = {miR-21 Gene Expression Triggered by AP-1 Is Sustained through a Double-Negative Feedback Mechanism}, url = {http://dx.doi.org/10.1016/j.jmb.2008.03.015}, volume = {In Press, Corrected Proof} }

TY - JOUR ID - citeulike:2644067 L3 - citeulike-article-id:2644067 TI - miR-21 Gene Expression Triggered by AP-1 Is Sustained through a Double-Negative Feedback Mechanism JF - Journal of Molecular Biology VL - In Press, Corrected Proof N2 - 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. KW - ap-1 KW - function KW - mir-21 KW - mirna KW - nfkappab AU - Fujita, Shuji AU - Ito, Taiji AU - Mizutani, Taketoshi AU - Minoguchi, Shigeru AU - Yamamichi, Nobutake AU - Sakurai, Kouhei AU - Iba, Hideo UR - http://dx.doi.org/10.1016/j.jmb.2008.03.015 ER -