SV40 PolyA (Simian virus 40 PolyA, also called PolyA) sequence is DNA sequence 
(240 bp) that possesses the activity of transcription termination and can add 
PolyA tail to mRNA. PolyA contains AATAAA hexanucleotide polyadenylation signal. 
Fourteen copies of Alu in sense orientation (Alu14) were inserted downstream of 
GFP in pEGFP-C1 to construct pAlu14 plasmid, and then HeLa cells were 
transiently transfected with pAlu14. Northern blot and fluorescence microscope 
were used to observe GFP RNA and protein expressions. Our results found that Alu 
tandem sequence inhibited remarkably GFP gene expression, but produced 
higher-molecular-mass GFP fusion RNA. PolyA and its sequence that was deleted 
AATAAA signal in sense or antisense orientation were inserted between GFP and 
Alu tandem sequence in pAlu14. The results showed that all the inserted PolyA 
sequences partly eliminated the inhibition induced by Alu14. PolyA sequences 
without AATAAA signal in sense or antisense orientation still induced 
transcription termination. Antisense PolyA (PolyAas) was divided into four 
fragments that all are 60 bp long and the middle two fragments were named 2F2R 
and 3F3R. 2F2R or 3F3R was inserted upstream of Alu tandem sequence in pAlu14. 
The molecular mass of GFP fusion RNA increased when the copy number of 2F2R 
increased. 2F2R can support transcription elongation when 2F2R is located 
upstream of other 2F2R. Nevertheless, 2F2R located upstream of Alu tandem 
sequence can induce transcription termination. Inserting one copy or 64 copies 
of 3F3R in upstream of Alu tandem sequence caused the production of 
lower-molecular-mass GFP RNA.