The U4/U6.U5 tri-snRNP is a key component of spliceosomes. By using chemical reagents and RNases, we performed the first extensive experimental analysis of the structure and accessibility of U4 and U6 snRNAs in tri-snRNPs. These were purified from HeLa cell nuclear extract and Saccharomyces cerevisiae cellular extract. U5 accessibility was also investigated. For both species, data demonstrate the formation of the U4/U6 Y-shaped structure. In the human tri-snRNP and U4/U6 snRNP, U6 forms the long range interaction, that was previously proposed to be responsible for dissociation of the deproteinized U4/U6 duplex. In both yeast and human tri-snRNPs, U5 is more protected than U4 and U6, suggesting that the U5 snRNP-specific protein complex and other components of the tri-snRNP wrapped the 5' stem-loop of U5. Loop I of U5 is partially accessible, and chemical modifications of loop I were identical in yeast and human tri-snRNPs. This reflects a strong conservation of the interactions of proteins with the functional loop I. Only some parts of the U4/U6 Y-shaped motif (the 5' stem-loop of U4 and helix II) are protected. Due to difference of protein composition of yeast and human tri-snRNP, the U6 segment linking the 5' stem-loop to the Y-shaped structure and the U4 central single-stranded segment are more accessible in the yeast than in the human tri-snRNP, especially, the phylogenetically conserved ACAGAG sequence of U6. Data are discussed taking into account knowledge on RNA and protein components of yeast and human snRNPs and their involvement in splicesome assembly.

• PMID: 11955014
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Reference Type

Journal Article | Research Support, Non-U.S. Gov't

Authors

Mougin A, Gottschalk A, Fabrizio P, Lührmann R, Branlant C

Primary Lit For

U6 small nuclear ribonucleoprotein complex | U4/U6.U5 tri-small nuclear ribonucleoprotein complex | U5 small nuclear ribonucleoprotein complex

Additional Lit For

SNR14 | SNU114 | SMX2 | SMD1 | SNR6 | PRP31 | PRP8 | PRP28 | LSM8 | BRR2 | SNR7-L | ... Show allSNR7-S | SMB1 | SNU13 | LSM2 | PRP6 | LSM6 | SAD1 | SMD2 | PRP4 | SMX3 | LSM4 | PRP3 | LSM5 | SME1 | DIB1 | LSM7 | SNU66 | SMD3 Show fewer

Review For