Скачать с ютуб 2.3 Many oncogenes have human origin в хорошем качестве

2.3 Many oncogenes have human origin

Human Oncogenes in tumor cell are related to those carried by transforming retroviruses The myc oncogene, originally known from its presence in avian myelocytomatosis virus was found to be present in multiple copies in the DNA of the HL60 human promyelocytic leukemia cell line. The multiple copies of this gene caused proportionately increased levels of its protein product; this somehow favored the proliferation of the cancer cells. The erbB gene, first discovered through its presence in the genome of avian erythroblastosis virus was discovered to be present in increased copy number in tumor cells of the DNAs of human stomach, breast, and brain. Mutant alleles of the sic oncogene, the first viral oncogene to be discovered were found in the genomes of human tumor cells, specifically, in the genomes of 12% of advanced human colon carcinomas. Inappropriate activation of proto oncogenes Consider a proto-oncogene acquired by a retrovirus. After insertion into the retrovirus genome, expression of this captured human gene was controlled by a retroviral transcriptional promoter which invariably drove the human gene’s expression unceasingly and at high levels. Transcription of this gene, now an oncogene, was no longer responsive to the cellular signals that had previously regulated its expression. Once present in the genome of avian myelocytomatosis virus (AMV), expression of this gene (now called v- myc) is found to be at far higher levels than are seen normally in cells, and this expression occurs at a constant (sometimes termed constitutive) level.