Biology 2581B Lecture Notes - Lecture 3: Oncogene, Reverse Transcriptase, Point Mutation
Document Summary
Cancer can also be caused by viruses: dna tumor viruses: cause cancer because accidentally a part of their gene is incorporated into the genome. Oncogenes are integral parts of the viral genome and are required for viral replication by stimulation cell growth and proliferation: retroviruses: usually cause cancer by inserting an oncogene in the genome by reverse transcriptase from rna to dna. Oncogenes are derived from normal cellular genes and have no function for the virus except to allow proliferation in tumors. Can be slow or fast: slow-acting retroviruses: long latency, weakly oncogenic, only cause cancer after months/years, lack an oncogene. Other drivers of tumorigenesis: hyper/hypomethylation: mutations affecting epigenetic regulators, such as changes in the activity of histone-modifying enzymes or chromatin-remodeling complexes. Tumors typically harbor only a single mutated allele of a gene encoding a chromatin-modifying enzyme (haplo-insufficient). Losing both alleles would kill the cell: tet dna hydroxylases: catalyses conversion of 5-methylcytosine to 5- hydroxylmethylcytosine.