Advanced Look --> 2.) Pol
II (RNA Polymerase II)
RNA Polymerase II (Pol II)
is the complex responsible for reading the DNA template and creating a complementary
mRNA copy. In order for Pol II to begin this process, several general transcription
factors must first help to position and activate the Pol II complex.
Clicking on each of the thumbnail images will bring up a larger, labeled version
of the described scene.
see the Flash movie for the following sequence of images,
Two smaller general transcription factors
are shown coming into view:TFIIA (orange) and
TFIIA binds to the TATA-box near TFIID.
TFIIB approaches the TATA-box. The Pol II complex is
being assembled in the distance.
TFIIB binds to the TATA-box and TFIID. It is thought
to help the Pol II complex bind correctly.
The Pol II complex has been assembled and is approaching
the start site for transcription.
Aided by the general transcription factors already in
place, Pol II binds to the DNA strand at the start site for transcription.
TFIIE is show approaching from the right.
Additional factors must still bind to the complex in
order to start transcription. Here, TFIIE has already bound (olive green)
and TFIIH (red) is preparing to do the same.
Once all of the general transcription factors are bound,
energy, in the form of ATP (blue/pink), is needed to activate the Pol II