Connecting transcription of small nuclear RNA genes with RNA 3 end formation . (360G-Wellcome-081312_Z_06_Z)

The 3 ends of human small nuclear (sn)RNAs synthesized by RNA polymerase II (pol II) are formed by RNA processing directed by the snRNA gene-specific 3 box. In living cells (in vivo), processing occurs efficiently only when transcription is initiated from an snRNA promoter. Our findings indicate that termination of transcription, in turn, requires recognition of the 3 box. However, the molecular mechanism of 3 box-dependent processing and the link between processing and transcription remain to be elucidated. We have shown that the carboxy-terminal domain (CTD) of pol II and its phosphorylation are required for 3 box function and a large pol II CTD-associated complex has recently been implicated in snRNA 3 end formation. In addition, we very recently succeeded in setting up an in vitro 3 box-dependent processing system. These advances pave the way for analysis of this important but, as yet, poorly characterized processing reaction. The key goals of the proposed research are to id entify the factors required for accurate 3 box-dependent RNA processing and to define the interactions with the transcription machinery that couple this processing reaction to transcription.