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Ting Su, Ashrafali Mohamed Ismail, Meeta Mistry, Donald Seto, David W. Dyer, James Chodosh, Jaya Rajaiya; OCT4 and YY1 transcription factors regulate gene expression of an adenoviral ocular pathogen. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1954.
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© ARVO (1962-2015); The Authors (2016-present)
There are about 20 million ocular adenoviral cases per year in the United States. Epidemic keratoconjunctivitis (EKC) is the most highly contagious and most severe of these. EKC manifests with acute membranous keratoconjunctivitis and delayed-onset of corneal stromal infiltrates. Transcription factors (TFs) are sequence-specific DNA binding proteins. As intracellular parasites, viruses hijack host cellular proteins, including TFs, to control their gene expression and replication. We investigated the role of host TFs in the transcriptional regulation of a major EKC pathogen - human adenovirus species D type 37 (HAdV-D37).
We first performed in silico TRANSFAC database analysis to identify TF candidates for binding to the HAdV-D37 genome. Next, chromatin immunoprecipitation and high-throughput sequencing (ChIP-Seq) were performed in virus-infected A549 cells, including the TF YY1, previously reported to bind E1A. From the high-throughput sequencing reads (HiSeq 2500 system, illumina), motif analysis was performed, and the specific TF-viral DNA binding sites were validated by electrophoretic mobility shift assays (EMSA). Gene expression was studied in the setting of both TF-siRNA knockdown and overexpression, using RT-qPCR for viral transcripts spanning the whole genome.
In silico analysis showed OCT4 as the TF with greatest binding affinity for the HAdV-D37 genome. By ChIP-Seq analysis, OCT4 and YY1 were shown to directly bind the viral DNA motifs, ATTTGCAT and CGCCATCTT, respectively, present in the non-coding regions of the inverted terminal repeat (ITR) and adjacent to E4 target genes. Both OCT4 and YY1 were shown to repress E3 (immune evasion genes) expression. Additionally, YY1 knockdown upregulated viral early gene expression, including E1B, E2A, and E2B.
OCT4 and YY1 directly bind to HAdV-D37 and downregulate E3 gene expression, potentially modulating host immune responses to infection. Our findings provide novel functions for non-coding viral DNA; in depth understanding of viral gene expression offers a unique perspective to treatment of ocular viral disease.
This is a 2021 ARVO Annual Meeting abstract.
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