The novel COVID-19 virus continues to wreak havoc among all people in the world. Several studies have done and still the demand is huge to tackle the devastating condition. One of the latest updates in the research world is something that came out due to the unusual findings by the healthcare workers. It states that the patients who completely recovered from COVID-19 were tested positive in the PCR test. The test was made after weeks or months, indicating the recovery. To our surprise, many of these patients do not appear to shed the infectious virus. Recently, a paper published by the Proceeding National Academy of Science, USA shows that SARS-CoV-2 can be reverse transcribed and integrated into the DNA of human cells through a process called Reverse Transcription. These integrated genomes are then read into RNA which can give positive PCR results.
This is not only the case for SARS-CoV-2(non-retro) virus. Rather many other viruses gets a part and around 8% of human’s DNA consists of remnants of old viruses. Keeping this hypothesis, researchers infected human cells with coronavirus and sequenced the DNA to check the presence of viral material. Three DNA sequencing techniques were used to detect the genomic SARS-CoV-2 sequence and integration into the genome of infected cell, which include Nanopore long-read sequencing, Illumina paired-end whole genomic sequencing, and Tn5 tagmentation. While examining the viral sequences in the DNA of a sample, researchers found the hallmark of a genetic feature called Retrotransposons/jumping genes (Transposons are sections of DNA that can move from one region of the genome to another). One common transposon in the human genome is the Long Interspread Nuclear Element 1 (LINE1) retrotransposon. They found that target site duplication flanking the viral sequences and consensus (LINE1) endonuclease recognition segment at the integration site.
Also, researchers on analyzing published datasets of an RNA transcript from samples of different types of COVID- 19 patients were able to calculate the fraction of genes that were transcribed in these patient’s cells and contained viral sequences, which could be derived from integrated viral proteins. Therefore, the integration and transcription of viral sequences may contribute to the detection of viral RNA by PCR in patients after infection and clinical recovery.
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Source: Medical Xpress