TY  - GEN
TI  - Analysis of the miRNA-mediated regulation of AP-1 in non-tumorigenic and tumorigenic HPV18-positive cell lines
Y1  - 2009///
KW  - AP-1 
KW  -  miRNA 
KW  -  HPV18 
KW  -  carcinogenesis 
KW  -  transformation
N2  - The transcription factor AP-1 is built up by dimerization of Jun and Fos family members and regulates major biological events like proliferation, invasion and apoptosis. The dimeriza-tion pattern of AP-1 changes when HPV-positive cells undergo malignant progression. While in HPV-positive non-malignant cells (?444?) AP-1 is composed of c-Jun/Fra-1, their malignant counterparts (?CGL3?) mainly express c-Jun/c-Fos heterodimers. Since microRNAs (miRNA), a potent group of post-transcriptional regulators, are often deregulated during malignant trans-formation, the regulation of AP-1 by miRNAs during cancer progression was analyzed. For this purpose, Drosha and Dicer, the key processing proteins in miRNA biogenesis, were knocked down by siRNAs. Quantitative RT-PCRs and Western blots showed that Fra-1 was regulated by miRNAs in non-tumorigenic and tumorigenic hybrids, but not in parental tumorigenic HeLa cells. c-Jun is repressed by miRNAs only in 444 and HeLa cells, but not in CGL3 cells, which express only low amounts of c-Jun. Conversely, c-Fos is indirectly up-regulated by miRNAs in HeLa cells. As analyzed by electro-mobility-shift / super shift-assays, the observed changes in protein expressions also resulted into modulations of AP-1 dimer composition that were also confirmed by AP-1 responsive Luciferase assays (TRE-Luc). Furthermore, reporter constructs harboring the 3?UTRs of c-Jun and Fra-1 showed direct regula-tion by miRNAs throughout the full-length 3?UTRs suggesting multiple miRNA binding sites and / or multiple regulatory miRNAs. Using an ?Illumina? miRNA expression array, differentially expressed miRNAs in the non-tumorigenic and tumorigenic cell hybrids were detected and matched with miRNAs that were predicted to regulate c-Jun according to a bioinformatics analysis with PicTar, TargetScan, miRBase and DIANA microT. The data pointed towards miR-495 as one regulatory miRNA targeting c-Jun. Preliminary luciferase assays with over-expressed miR-495 did not reveal an interaction with a reporter construct harboring c-Jun 3?UTR. Other potential candidates were not tested. These results show for the first time that c-Jun and Fra-1 are direct targets of miRNAs and that c-Fos is submitted to an indirect miRNA regulation, thereby expanding known miRNA-c-Fos regulatory circuits. Moreover, it is demonstrated that miRNAs can modulate AP-1 composition and transcriptional activity in cervical carcinoma cells with potential consequences on AP-1 target genes. 
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/10368/
A1  - Sobel, Matthias
ID  - heidok10368
AV  - public
ER  -