circularized mRNA for translation - Does the mRNA relinearize after large subunit docking? (Aug/30/2007 )
I am working on an animation illustrating gene expression. I am hoping to represent the configuration of the RNA during translation as accurately as possible (while still clearly communicating the main ideas). Is the following sequence correct?
During cap-dependent translation initiation, poly-A associates through poly-A binding proteins (PABP) with eukaryotic initiation factor 4G (eIF4G) and some other initiation factors.
This makes the mRNA form a loop.
Once the small subunit moves toward the start codon, it takes along eIF4G (I gather from the figure on this page):
This implies that the circularized mRNA is forming a lariat-like structure, with the single stem of the lariat getting longer as the small subunit moves farther from the 5'-cap of the mRNA.
What happens when the large ribosomal subunit binds? Based on the wikipedia illustration cited above, I would expect that eIF4G falls off the RNA and so the lariat opens, recircularizing later for the next round of translation.
<PABP binds eIF4G>
<initiation complex scans for start codon>
<large subunit of ribosome binds>
Thanks for any suggestions or pointers toward a clearer story!
I'm replying to my own post in hopes that by moving it to the top of the queue, someone will see my original question and help me out.