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Cancer and viruses http://biochemistry4all.com/Taha/4.htm Virus: is a small infectious agent that can replicate only inside the living cells of organisms An oncovirus: is a virus that can cause cancer All retroviruses have three major coding domains; gag, pol and env In the gag region of the virus, the synthesis of the internal virion proteins are maintained which make up the matrix, capsid and nucleocapsid proteins In pol, the information for the reverse transcription and integration enzymes are stored In env, it is derived from the surface and transmembrane for the viral envelope protein There is a third coding domain which is smaller, but exists in all retroviruses Pol is the domain that encodes the virion protease 1- DNA viruses 2- RNA viruses Two model for cancer – producing agents: 1-SV40 (simian vaculating virus 40) The papova – viruses Tool for studying how a normal cell become malignant In monkey cell culture Hamster and SV40 2-Adenovriuses Named for human adenoid cells Found in nearly everyone's upper respiratory tract 33 types are known Grouped according to their cancer – producing activity in hamster: ◦ group A ◦ group B ◦ group C Makeup of these viruses: outer protein covering shaped is like icosahedrons DNA SV40 carries 3 genes vs Adenoviruses 30 genes vs bacteria 5000 genes Chemically altering a virus DNA Viruses replicate in cells: Entering the cell The viral DNA is transported to the cell nucleus mRNA viral proteins Viral proteins cell nucleus viral chromosomes viral chromosomes mRNA protein coats protein coats cell nucleus viral chromosomes Dependence on host cell Orderly control Normal cell Malignant Entering the cell The viral DNA is transported to the cell nucleus mRNA viral proteins Viral proteins cell nucleus viral chromosomes Viral chromosomes mRNA protein coats Protein coats cell nucleus viral chromosomes Dependence on host cell Orderly control Normal cell Malignant Virus Percent of cancers[ Associated cancer types Hepatitis viruses, including hepatitis B (HBV) and hepatitis C (HCV) Human T-lymphotropic virus (HTLV) 4.9 Hepatocellular carcinoma (liver cancer). 0.03 Tropical spastic paraparesis and adult T-cell leukemia Human papillomaviruses (HPV) 5.2 Kaposi’s sarcoma-associated herpesvirus 0.9 Merkel cell polyomavirus NA Cancers of cervix, anus, penis, vulva/vagina, and some cancers of the head and neck. Kaposi’s sarcoma, multicentric Castleman's disease and primary effusion lymphoma Merkel cell carcinoma Epstein–Barr virus (EBV) NA Burkitt’s lymphoma, Hodgkin’s lymphoma, post-transplantation lymphoproliferative disease and Nasopharyngeal carcinoma.
