BIOL 1st Edition Lecture 22 Outline of Last Lecture I Split Genes and RNA Processing II MicroRNAs and Gene Expression III Mutations IV Viruses V Types of Viruses Outline of Current Lecture I Cancer II Oncogenes and Proto Oncogenes III Tumor Suppressor Genes IV MicroRNAs Current Lecture Molecular Biology of Cancer Cells I Cancer a Definition set of diseased in which cells escape the control mechanisms that normally limit cell division b It is associated with mutations that affect gene expression c Often many mutations in different genes are needed to produce all of the characteristics of cancer d Altered expression of mircoRNAs is common e Two major classes of protein coding genes are mutated or have altered expression in cancer i Oncogenes or proto oncogenes ii Tumor suppressor genes II Oncogenes and Proto Oncogenes a Onco Greek for tumor b Certain retroviruses causes cancer because they have oncogenes that promote cell division c Proto oncogenes normal cells found to have genes similar to viral oncogenes i Genes that can cause cancer if expressed at too high level or without proper controls ii Example RAS a signaling protein that turns on cell cycle in response to growth factors in cancer RAS signaling occurs all the time even in the absence of growth factor d RAS is mutated in 30 of human cancers III Tumor Suppressor genes a Normal product inhibits cell division b A mutation that decreases the normal activity of a tumor suppressor may contribute to cancer c Example P53 guardian angel of the genome i DNA damage turns on P53 expression ii P53 is a transcription factor that turns on P21 iii P21 decreased the cell cycles thus allowing time to repair DNA iv If DNA damage is too much P53 tunes on a process called apoptosis cell suicide d P53 is mutated in 50 of cancers IV MicroRNAs a Small RNAs that are master regulators of cell division b Tumor suppressor miRNAs promising therapy to cancer i Some miRNAs are lost in cancer cells ii Tumor suppressor miRNAs replace the miRNAs that are lost and block the cancer c Oncogenic miRNAs onco miRs miRNAs that are over expressed in cancer and promote the disease
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