Analysis of Cellular Transcriptomic Changes Induced by Merkel Cell Polyomavirus miRNA
Merkel cell carcinoma (MCC) is a highly aggressive skin cancer with rising global incidence. Merkel cell polyomavirus (MCV) was discovered in 2008 in 80% of MCC samples and since then a causal link between MCV and the majority of MCC cases has been established. microRNAs (miRNA, miR) are a family of small non-coding RNAs which play a key role in post-transcriptional regulation of gene expression and are considered significant players in disease and development in many species. Whilst the focus of MCV research has thus far been on the oncogenic MCV early proteins, large tumour (LT) and small tumour (sT) antigens, there is a knowledge gap regarding MCV miRNA and its functional significance in MCV pathogenesis. Given the emerging importance of viral miRNAs in virus-host interaction and pathogenesis, the aim of this doctoral research project was to investigate alterations in host cell transcripts induced by MCV miRNA and determine any functional significance these might have on virus-host cell interaction. RNA sequencing (RNA-Seq) in the presence and absence of MCV miRNA uncovered a multitude of downregulated cellular transcripts. Gene ontology analysis revealed that MCV miRNA targets transcripts associated with multiple cellular processes, however, regulation of immune response was overrepresented in our datasets. Validation of RNA-Seq data using MCV miRNA mimics and a synthetic, fully replicative MCV genome (MCVSyn) confirmed RNA-Seq data at mRNA and protein expression level for several targets, including the cytokine stimulating gene, SP100, and the neutrophil stimulator chemokine, CXCL8. Moreover, dual luciferase assays revealed that SP100 and MAPK10 (a member of mitogen-activated protein kinases (MAPK) family which is involved in regulation of CXCL8 expression) are directly and specifically targeted and downregulated by MCV miRNA. The MCV miRNA-dependent dysregulation of CXCL8 secretion is associated with impaired neutrophil migration, suggesting that the virus miRNA may be implicated in evasion of the host immune response.
Virus, Cancer, Merkel cell carcinoma (MCC), Merkel cell polyomavirus (MCV), microRNA (miRNA)
Networked Digital Library of Theses and Dissertations