A Comprehensive Analysis of Argonaute-CLIP Data Identifies Novel, Conserved and Species-Specific Targets of miR-21 in Human Liver and Hepatocellular Carcinoma

• Main Authors: Aaron Balasingam Koenig, Juan Martín Barajas, María Jose Guerrero, Kalpana Ghoshal
• Format: Article
• Language: English
• Published: MDPI AG 2018-03-01
• Series: International Journal of Molecular Sciences
• Subjects: miRNA; miR-21; liver cancer; HCC
• Online Access: http://www.mdpi.com/1422-0067/19/3/851

MicroRNAs are ~22 nucleotide RNAs that regulate gene expression at the post-transcriptional level by binding messenger RNA transcripts. miR-21 is described as an oncomiR whose steady-state levels are commonly increased in many malignancies, including hepatocellular carcinoma (HCC). Methods known as cross-linking and immunoprecipitation of RNA followed by sequencing (CLIP-seq) have enabled transcriptome-wide identification of miRNA interactomes. In our study, we use a publicly available Argonaute-CLIP dataset (GSE97061), which contains nine HCC cases with matched benign livers, to characterize the miR-21 interactome in HCC. Argonaute-CLIP identified 580 miR-21 bound target sites on coding transcripts, of which 332 were located in the coding sequences, 214 in the 3′-untranslated region, and 34 in the 5′-untranslated region, introns, or downstream sequences. We compared the expression of miR-21 targets in 377 patients with liver cancer from the data generated by The Cancer Genome Atlas (TCGA) and found that mRNA levels of 402 miR-21 targets are altered in HCC. Expression of three novel predicted miR-21 targets (CAMSAP1, DDX1 and MARCKSL1) correlated with HCC patient survival. Analysis of RNA-seq data from SK-Hep1 cells treated with a miR-21 antisense oligonucleotide (GSE65892) identified RMND5A, an E3 ubiquitin ligase, as a strong miR-21 candidate target. Collectively, our analysis identified novel miR-21 targets that are likely to play a causal role in hepatocarcinogenesis.