Efficient synthesis of many small abundant RNAs is achieved by the proficient 
recycling of RNA polymerase (pol) III and stable transcription complexes. 
Cellular Alu and related retroposons represent unusual pol III genes that are 
normally repressed but are activated by viral infection and other conditions. 
The core sequences of these elements contain pol III promoters but must rely on 
fortuitous downstream oligo(dT) tracts for terminator function. We show that a 
B1-Alu gene differs markedly from a classical pol III gene (tRNAiMet) in 
terminator sequence requirements. B1-Alu genes that differ only in terminator 
sequence context direct differential RNA 3' end formation. These genes are 
assembled into stable transcription complexes but differ in their ability to be 
recycled in the presence of the La transcription termination factor. La binds to 
the nascent RNA 3' UUUOH end motif that is generated by transcriptional 
termination within the pol III termination signal, oligo(dT). We found that the 
recycling efficiency of the B1-Alu genes is correlated with the ability of La to 
access the 3' end of the nascent transcript and protect it from 3'-5' 
exonucleolytic processing. These results illuminate a relationship between RNA 
3' end formation and transcription termination, and La-mediated reinitiation by 
pol III.