The proto-oncogene can become an oncogene by a relatively small modification of its original
function. There are three basic activation types:
*A mutation within a proto-oncogene can cause a change in the protein structure, causing
- an increase in protein (enzyme) activity
- a loss of regulation
* An increase in protein concentration, caused by
- an increase of protein expression (through misregulation)
- an increase of protein (mRNA) stability, prolonging its existence and thus its activity in the
cell
- a gene duplication (one type of chromosome abnormality), resulting in an increased amount
of protein in the cell
*A chromosomal translocation (another type of chromosome abnormality), causing
- an increased gene expression in the wrong cell type or at wrong times
- the expression of a constitutively active hybrid protein. This type of aberration in a dividing
stem cell in the bone marrow leads to adult leukemia
Mutations in microRNAs can lead to activation of oncogenes. New research indicates that small RNAs 21-25 nucleotides in length called microRNAs (miRNAs) can control expression of these genes by downregulating them. Antisense messenger RNAs could theoretically be used to block the effects of oncogenes.
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Tags: activation, protooncogene