Viral Oncogenesis

Ifrah Ishaq University Of The Punjab, Lahore.

outlineOncogeneViral OncogenesisTypes Of Oncogenesis Viruses

• DNA Viruses• RNA Viruses

RetrovirusesLife Cycle Of RNA VirusConclusion

introductionOncogeneA region of the viral genome that can cause a tumor.

Proto-oncogene Genes that are found in all cells and its homologous is carried by a virus ( viral-oncogene).

• Viral OncogeneGenes in the viral genome; change host cell

proliferation control• Tumor-suppressor Genes Genes whose products inhibit cell

multiplication• Mutator Genes Genes whose products ensure accurate

DNA replication and DNA repair

Oncogenic Viruses

Oncogenic viruses are significant pathogens for humans, farm animals, and pets. These pathogens are classified into different virus families such as Hepadnaviridae, Flaviviridae, and Retroviridae.

Oncogenic viruses (tumor viruses) consist of both DNA and RNA viruses

Types of Oncogenesis Viruses

DNA VirusesVirus can containing either single stranded or double stranded DNA.

Examples of DNA viruses are:Adenoviridae, Herpesviridae, Papillomaviridae, Polyomaviridae, Poxviridae etc.

RNA Viruses RNA virus contains predominantly single stranded RNA; although viruses do exist that contain double stranded.

Examples of RNA viruses:Alpharetrovirus,Deltaretrovirus, Gammaretrovirus, Retroviridae, Flaviviridae etc.

Retroviruses

All oncogenic RNA viruses are retroviruses. In 1961, Rous sarcoma virus. Retroviruses have 3 basic genes

1. Gag2. pol3. env

Life Cycle of RNA VirusesSteps of life cycle explained below:1.Approaches the cell membrane 2.Receptors on the lipid bilayer(binding)3.Virus fuses with plasma membrane of the cell4.Role of reverse transcriptase 5.Role retroviral integrase6.Transcription of the viral DNA7.Viral RNA as well as the viral proteins; move outward8.Once outside, the virus matures

Diagram representation

Continued……

Plus-Strand RNA Virusesserve directly as mRNA ; translated into proteins.

Minus-Strand RNA Virusestranscribed into the mRNA ; then translated.

Conclusion

Many retroviruses do not have viral oncogenes. They integrate near some of the proto-oncogenes, activate their expression by pro-viral insertional mutagenesis, and modulate growth and differentiation of the host cells.

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