We describe the identification and characterization of circular intronic long 
noncoding RNAs in human cells, which accumulate owing to a failure in 
debranching. The formation of such circular intronic RNAs (ciRNAs) can be 
recapitulated using expression vectors, and their processing depends on a 
consensus motif containing a 7 nt GU-rich element near the 5' splice site and an 
11 nt C-rich element close to the branchpoint site. In addition, we show that 
ciRNAs are abundant in the nucleus and have little enrichment for microRNA 
target sites. Importantly, knockdown of ciRNAs led to the reduced expression of 
their parent genes. One abundant such RNA, ci-ankrd52, largely accumulates to 
its sites of transcription, associates with elongation Pol II machinery, and 
acts as a positive regulator of Pol II transcription. This study thus suggests a 
cis-regulatory role of noncoding intronic transcripts on their parent coding 
genes.