We previously demonstrated that pseudogenes complementary to the small nuclear 
RNAs U1, U2 and U3 are dispersed and abundant in the human genome. Here we 
report that three pseudogenes (U1.101, U2.13 and U3.5) are flanked by perfect 
short direct repeats of 16 to 19 base pairs. In all three pseudogenes. the 
upstream direct repeat abuts a DNA sequence corresponding to the 5' end of the 
mature snRNA; in U2.13 and U3.5, the downstream direct repeat immediately 
follows the truncated 3' end of the snRNA sequence, whereas in U1.101, the 
downstream direct repeat is separated from the 3, end of the full-length snRNA 
sequence by a short A-rich region. We consider the direct repeats to be an 
indication that these three pseudogenes were created by insertion of snRNA 
information into a new chromosomal locus. To explain why the upstream repeat 
abuts a DNA sequence complementary to the 5' end of the mature snRNA, we propose 
a model for insertion that uses a reverse transcript of the snRNA as an 
intermediate. Furthermore, we note similarities between the structure of all 
three pseudogene loci and the Alu family of middle repetitive DNA sequences. 
These similarities suggest that some Alu family sequences are mobile genetic 
elements that can transpose to new chromosomal loci using as an intermediate a 
cDNA copy of an RNA transcribed from the Alu family element by RNA polymerase 
III.