Editing Transactivation (section)

== Natural transactivation ==
Transactivation can be triggered either by endogenous cellular or viral proteins, also called '''transactivators'''.  These protein factors [[Trans acting|act in trans]] (''i.e.'', [[intermolecular]]ly). [[HIV]] and [[HTLV]] are just two of the many viruses that encode transactivators to enhance viral gene expression. These transactivators can also be linked to cancer if they start interacting with, and increasing expression of, a cellular [[proto-oncogene]]. HTLV, for instance, has been associated with causing [[leukemia]] primarily through this process. Its transactivator, [[Tax gene product|''Tax'']]'','' can interact with [[p40 gene|p40]], inducing overexpression of [[interleukin 2]], [[interleukin receptor]]s, [[GM-CSF]] and the [[transcription factor]] [[c-Fos]]. HTLV infects [[T-cell]]s and via the increased expression of these stimulatory [[cytokines]] and [[transcription factors]], leads to uncontrolled proliferation of T-cells and hence [[lymphoma]].