The Effects of Cytidine Deaminases on Cellular Transformation
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The apolipoprotein B RNA-editing cytidine deaminase (APOBEC) family of proteins is made up of 10 members, all of which possess a common DNA/IRNA editing motif which enables them to act directly on intracellular cytosine to cause a cytosine to guanine mutation. Activation induced cytidine deaminase (AID) is found within B lymphocytes within the cell, and has been shown indispensable to both class switch recombination (CSR) and somatic hypermutation (SHM). APOBEC3G is found primarily within T lymphocytes, where it plays a role in retroviral defense by massively deaminating the newly formed retroviral DNA as it exits the infected cell. The natural function of these two proteins as DNA mutators has led to investigations into their possible roles as cancer causing agents. Previous studies have shown that both of these proteins can cause mammalian cells to become cancerous, and overexpression of these proteins has been found in certain types of cancer, but no studies have been published on the effects of these proteins within human cells to date. The goal of this study was to use an anchorage independent growth assay of 293 human kidney cells which had been transfected with one of the proteins to determine the transformational properties, if any, of these proteins on human cells in vitro, and to determine the level of expression of the transfected proteins within the cultured cells using RT-PCR. It was hypothesized that the overexpression of these proteins would cause cellular transformation, and that a higher level of expression would lead to a higher rate of transformation within the cell. The results of the study were inconclusive due to the apparent ability of the 293 cells to survive under anchorage independent conditions and an inability to determine the level of protein expression using RT-PCR.