A Comprehensive Analysis of Argonaute-CLIP Data Identifies Novel, Conserved and Species-Specific Targets of miR-21 in Human Liver and Hepatocellular Carcinoma
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Authors: Koenig, Aaron Balasingam; Barajas, Juan Martin; Guerrero, Maria Jose; Ghoshal, Kalpana
Abstract
MicroRNAs are similar to 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.
Comparative genomic hybridization analysis of Y79 and FISH mapping indicate the amplified human mitochondrial ATP synthase alpha-subunit gene (ATP5A) maps to chromosome 18q12->q21
CYTOGENETICS AND CELL GENETICS
Authors: Godbout, R; Pandita, A; Beatty, B; Bie, W; Squire, JA
Abstract
The four mitochondrial ATP synthase a-subunit (ATP5A) genes map to chromosomes 2, 9, 16, and 18. In this study we have refined the localization of two of these genes by fluorescence in situ hybridization (FISH) to metaphase spreads, and further characterised the involvement of ATP5A in the amplification process in the retinoblastoma cell line Y79. Comparative genomic hybridization (CGH) analysis of Y79 indicated that gene amplification was present on both the short arm of chromosome 2 and the long arm of chromosome 18. FISH indicated that the functional ATP5A gene mapped to 18q12-->q21, the same band location identified by CGH analysis of Y79. An ATP5A pseudogene (ATP5AP1) maps to 9p12. Gains in chromosomal material at 18q12-->q21 likely involve hybridization to amplified copies of the ATP5A gene while gains at 2p24 represent hybridization to the MYCN and DDX1 genes, also amplified in Y79.