The majority of the noncoding regions of mammalian genomes have been found to be 
transcribed to generate noncoding RNAs (ncRNAs), resulting in intense interest 
in their biological roles. During the past decade, numerous ncRNAs and aptamers 
have been identified as regulators of transcription. 6S RNA, first described as 
a ncRNA in E. coli, mimics an open promoter structure, which has a large bulge 
with two hairpin/stalk structures that regulate transcription through 
interactions with RNA polymerase. B2 RNA, which has stem-loops and unstructured 
single-stranded regions, represses transcription of mRNA in response to various 
stresses, including heat shock in mouse cells. The interaction of TLS 
(translocated in liposarcoma) with CBP/p300 was induced by ncRNAs that bind to 
TLS, and this in turn results in inhibition of CBP/p300 histone 
acetyltransferase (HAT) activity in human cells. Transcription regulator EWS 
(Ewing's sarcoma), which is highly related to TLS, and TLS specifically bind to 
G-quadruplex structures in vitro. The carboxy terminus containing the 
Arg-Gly-Gly (RGG) repeat domains in these proteins are necessary for 
cis-repression of transcription activation and HAT activity by the N-terminal 
glutamine-rich domain. Especially, the RGG domain in the carboxy terminus of EWS 
is important for the G-quadruplex specific binding. Together, these data suggest 
that functions of EWS and TLS are modulated by specific structures of ncRNAs.