In the absence of DNA, purified yeast RNA polymerase II can bind RNA to form a 
binary complex. RNA in such RNA-RNA polymerase complexes undergoes reactions 
previously thought to be unique to nascent RNA in ternary complexes with DNA, 
including TFIIS-dependent cleavage and elongation by 3'-terminal addition of NMP 
from NTP. Both of these reactions are inhibited by alpha-amanitin. Hence, by 
several criteria the RNA in binary complexes is bound to the polymerase in a 
manner quite similar to that in ternary complexes in which the catalytic site 
for nucleotide addition is positioned at or near the 3'-OH terminus of the RNA. 
These findings are consistent with a model for the RNA polymerase ternary 
complex in which the RNA is bound at the 3' terminus through two protein-binding 
sites located up to 10 nt apart.