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oncogene 541 one-turn recombination signal sequence
α Surface antigen
(AFP) is demonstrable in approximately 70% of hepatocellular
carcinomas.
oncogene
A gene linked to carcinogenesis when deregulated. Such
genes may encode positive regulators of cell growth. They
may be activated by mutation or retroviral integration. They
are involved in the control of cell growth and when defective
in structure or expression can lead to abnormal cell
proliferation resulting in tumor generation. Genes with the
capacity to induce neoplastic transformation of cells, they
are derived from normal genes (proto-oncogenes) or from
oncogenic RNA (oncorna) viruses. Their protein products
are critical for the regulation of gene expression and growth
signal transduction. Translocation, gene amplification, and
point mutation may lead to neoplastic transformation of
proto-oncogenes. Oncogenes may be revealed through the
use of viruses that induce tumors in animals or by derivation
of tumor-causing genes from cancer cells. The human
genome has more than 20 proto-oncogenes and cellular
oncogenes. An oncogene alone cannot produce cancer. It
must be accompanied by malignant transformation involving
multiple genetic steps. Oncogenes encode four types of
proteins, including growth factors, receptors, intracellular
transducers, and nuclear transcription factors.
oncogenesis
The process by which tumors develop.
oncogene theory
A concept of carcinogenesis that assigns tumor development
to latent retroviral gene activation through irradiation
RNA
virus
DNA
virus
Embryonic cell
(gene α is functional)
α Gene
Infected
cell
RNA
provirus
α Gene
repressed
Normal adult cell
(repressed α gene)
Oncofetal antigen.
Oncogenic virus.
α Surface antigen
Malignant adult cell
(de-repressed α gene)
α Gene
De-repressed
or carcinogens. These retroviral genes are considered to
be normal constituents of cells. Following activation, these
oncogenes are presumed to govern the neoplasm through
synthesized hormones and even the possible construction
of a complete oncogenic virus. This concept states that all
cells may potentially become malignant.
oncogenic virus
Any virus, whether DNA or RNA, that can induce malignant
transformation of cells. An example of a DNA virus is
human papillomavirus. Retroviruses are RNA viruses.
oncomouse
Commercially developed transgenic mice into which
human genes have been introduced to make the mice more
susceptible to neoplasia. Transgenic mice are used for both
medical and pharmaceutical research.
one gene, one enzyme theory (historical)
An early hypothesis that proposed that one gene encodes one
enzyme or other protein. Although basically true, it is now
known that one gene encodes a single polypeptide chain, and
it is necessary to splice out mRNA introns composed of junk
DNA before mRNA can be translated into a protein.
one-hit theory
A concept related to complement activation that states that
only a single site of preparation is necessary for red cell
lysis during complement-antibody-mediated injury to a cell
membrane.
one-turn recombination signal sequence
Immunoglobulin gene recombination signal sequence separated
by an intervening sequence of 12 base pairs.
Steady state
Integrated
Infectious RNA
virus and cell membrane
Tumor-specific
transplantation antigen
Leukemia
Virus-specific antigen
Malignancy
O