Help! Questions about transcriptional elements in SV40 'control' region

[A. M. Lotto]

Hello,
	I am in desperate need of an explanation of some transcriptional 
elements of SV40.  

<-- early   tata       21 bp repeats            72 bp segments
____________________________________________________________________________
   |        XXXX  |  21  |  21  | 21  | |     72       |     72       |
----------------------------------------------------------------------------
      Ori                                                       late -->


My questions regard the sequence of events.  Enhancers bind to TFIID.  
SP1 binds to GC boxes in 21 bp repeat sequences.  TFIID interacts with 
SP1 and SP1 interacts with RNA Pol II which doesn't know where to bind 
the DNA.  First, I am not entirely sure the previous sequence of events 
is even close to correct, secondly, how do these components interact to 
increase the efficiency of txn?  Where does TFIID bind?  My sources say 
that the enhancers bind to the 72 bp sequences but also that TFIID binds 
enhancers.   I am confused about this and would greatly appreciate anyone 
able to shed some light on these interactions.

Thanks very much.

Amy Lotto
aurelia at u.washington.edu