Im. Morgan et al., AMINO-ACID SUBSTITUTIONS MODULATE THE EFFECT OF JUN ON TRANSFORMATION, TRANSCRIPTIONAL ACTIVATION AND DNA-REPLICATION, Oncogene, 8(5), 1993, pp. 1135-1140
The retroviral oncogene v-jun and its cellular counterpart code for pr
oteins that function as major components of the transcription factor c
omplex AP-1. Jun proteins bind to the AP-1 consensus sequence as homod
imers or heterodimers with members of the Fos protein family. This rep
ort compares the ability of viral and cellular Jun proteins (v-Jun and
c-Jun) to activate transcription and to stimulate DNA synthesis. The
effect of amino acid substitutions on cellular transformation is also
described. In F9 cells c-Jun is a more effective transactivator than v
-Jun, which carries two amino acid substitutions in the carboxy-termin
al region that together down-regulate transactivation. The delta delet
ion, present in the amino-terminal region of v-Jun, does not affect tr
ansactivation in F9 cells; however, it does modulate the stimulation o
f DNA synthesis. When delta is deleted, the amino acid substitutions a
re without consequence on DNA synthesis. In the presence of delta the
amino acid substitutions down-regulate DNA synthesis. Deletion of the
Jun transactivation domain, which is required for cellular transformat
ion, abolishes both transactivation and stimulation of DNA synthesis.
We conclude that transformation, transactivation and stimulation of DN
A synthesis all depend on the presence of the transactivation domain.
The three functions are, however, not tightly correlated, and further
work is needed to define the role of the biochemical activities of Jun
in oncogenesis.