Cajal body finds its function

The Cajal body (CB, formerly coiled body) is a prominent nuclear structure, yet its function remains obscure. Now, Xavier Darzacq, Tamás Kiss (CNRS, Université Paul Sabatier, Toulouse, France), and colleagues speculate that the CB is where small nuclear RNAs go for modification.

Last year, Kiss's team identified a small guide RNA, U85, that directs both 2'-O- methylation and pseudouridylation of the spliceosomal component U5 snRNA. This year, they've identified six more RNAs, U87-U92, dubbed small Cajal body–specific RNAs, or scaRNAs.

The new scaRNAs resemble U85 in structure, and they contain sequences complimentary to pol II–transcribed UsnRNAs, suggesting that the scaRNAs may be guides for posttranscriptional modification of the UsnRNAs. The scaRNAs are immunoprecipitated by antibodies against fibrillarin and GAR, proteins that are likely to be involved in these modification reactions.

Most important, says Kiss, is the...