Research article

Systematic identification of non-coding RNA 2,2,7-trimethylguanosine cap structures in Caenorhabditis elegans

Dong Jia^{* 1,2} , Lun Cai^{* 3,4} , Housheng He^{* 1,4} , Geir Skogerbø¹ , Tiantian Li^1,4 , Muhammad Nauman Aftab^1,4 and Runsheng Chen¹

¹Bioinformatics Laboratory, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China

²Shanxi Agricultural University, Taigu, Shanxi, 030801, China

³Bioinformatics Research Group, Key Laboratory of Intelligent Information Processing, Institute of Computing Technology, Chinese Academy of Sciences, Beijing, 100080, China

⁴Graduate School of the Chinese Academy of Sciences, Beijing 100039, China

author email corresponding author email* Contributed equally

BMC Molecular Biology 2007, 8:86doi:10.1186/1471-2199-8-86

Published:	29 September 2007

Abstract

Background

The 2,2,7-trimethylguanosine (TMG) cap structure is an important functional characteristic of ncRNAs with critical cellular roles, such as some snRNAs. Here we used immunoprecipitation with both K121 and R1131 anti-TMG antibodies to systematically identify the TMG cap structures for all presently characterized ncRNAs in C. elegans.

Results

The two anti-TMG antibodies precipitated a similar group of the C. elegans ncRNAs. All snRNAs known to have a TMG cap structure were found in the precipitate, indicating that our identification system was efficient. Other ncRNA families related to splicing, such as SL RNAs and Sm Y RNAs, were also found in the precipitate, as were 7 C/D box snoRNAs. Further analysis showed that the SL RNAs and the Sm Y RNAs shared a very similar Sm binding site element (AAU_4–5GGA), which sequence composition differed somewhat from those of other U snRNAs. There were also 16 ncRNAs without an Sm binding site element in the precipitate, suggesting that for these ncRNAs, TMG formation may occur independently of Sm proteins.

Conclusion

Our results showed that most ncRNAs predicted to be transcribed by RNA polymerase II had a TMG cap, while those predicted to be transcribed by RNA plymerase III or located in introns did not have a TMG cap structure. Compared to ncRNAs without a TMG cap, TMG-capped ncRNAs tended to have higher expression levels. Five functionally non-annotated ncRNAs also have a TMG cap structure, which might be helpful for identifying the cellular roles of these ncRNAs.