You are studying cultured reindeer cells. The cells start out
being brownish gold, due to the activity of the FulL protein (that
we recently learned is induced by turkey extract). When you
incubate the cells with the extracellular factor Santa, there is a
rapid loss of FulL from the cells, and this loss causes the cells
to immediately go from being brown to being white. Treatment with
Santa also causes the reindeer cells to transcribe the snoW gene,
as well as other genes (treE, gifT, and belL). A few hours after
snoW, treE, gifT, and belL are transcribed and translated, the
cells secrete red and green pigments and also start gliding across
the culture dish. They also seem to prefer media with a higher
nutrient level, and they are distinctly larger. The new media
contains factors CookE and MilK, and after addition of either of
these, there are more cells in the dish after a few days.
  This effect of CookE and MilK can be inhibited by
exposure to strong sunlight (UV rays). Finally, you find another
factor, called Grinch, which will result in death of the reindeer
cells.

b. You look in the promoter regions of the snoW, treE, gifT, and
belL genes. You find one common 6 nucleotide sequence, which you
name the SRE (Santa responsive element). It is bound by the SREB
factor. Describe one mechanism by which Santa (an extracellular
factor) might activate SREB-include all of the necessary steps,
including when and how SREB becomes nuclear and other proteins
involved in the process.