A highly specific terminal uridylyl transferase modifies the 3'-end of U6 small nuclear RNA.
AUTOR(ES)
Trippe, R
RESUMO
HeLa cell extracts contain significant amounts of terminal uridylyl transferase (TUTase) activity. In a template-independent reaction with labeled UTP, these enzymes are capable of modifying a broad spectrum of cellular RNA molecules in vitro . However, fractionation of cell extracts by gel filtration clearly separated two independent activities. In addition to a non-specific enzyme, an additional terminal uridylyl transferase has been identified that is highly specific for cellular and in vitro synthesized U6 small nuclear RNA (snRNA) molecules. This novel TUTase enzyme was also able to select as an efficient substrate U6 snRNA species from higher eucaryotes. In contrast, no labeling was detectable with purified fission yeast RNA. Using synthetic RNAs containing different amounts of transcribed 3'-end UMP residues, high resolution gel electrophoresis revealed that U6 snRNA species with three terminal U nucleotides served as the optimal substrate for the transferase reaction. The 3'-end modification of the optimal synthetic substrate was identical to that observed with endogenous U6 snRNA isolated from HeLa cells. Therefore, we conclude that the specific addition of UMP residues to 3'-recessed U6 snRNA molecules reflects a recycling process, ensuring the functional regeneration for pre-mRNA splicing of this snRNA.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=147682Documentos Relacionados
- Mammalian U6 small nuclear RNA undergoes 3' end modifications within the spliceosome.
- A small RNA of Mycoplasma capricolum that resembles eukaryotic U6 small nuclear RNA.
- The highly conserved U small nuclear RNA 3'-end formation signal is quite tolerant to mutation.
- The 5' end of the coding region of a U6 RNA gene candidate from tomato starts with GUCC, a phylogenetically highly conserved 5' end sequence of U6 RNA.
- Nucleotide sequence of Physarum U6 small RNA.