Cryo-EM structure of human TUT1:U6 snRNA complex

Area of Science:

• Molecular Biology
• Structural Biology
• RNA Biology

Background:

• U6 small nuclear RNA (snRNA) is a ribozyme essential for pre-messenger RNA (pre-mRNA) splicing.
• Epitranscriptomic modifications, including oligo-uridylylation by terminal uridylyltransferase 1 (TUT1), occur on U6 snRNA.
• The 3'-oligo-uridylylated tail of U6 snRNA is vital for U4/U6 di-snRNP formation and efficient pre-mRNA splicing.

Purpose of the Study:

• To elucidate the structural basis of the interaction between human TUT1 and U6 snRNA.
• To understand how TUT1 specifically recognizes and binds U6 snRNA for oligo-uridylylation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structure of the human TUT1:U6 snRNA complex.

Main Results:

• The structure reveals how TUT1's multiple domains clamp and grip U6 snRNA, positioning its 3'-end in the catalytic pocket.
• Specific motifs and domains of TUT1, including the N-terminal zinc finger (ZF)-RNA recognition motif, catalytic Palm, Fingers, and C-terminal kinase-associated 1 domain, mediate the interaction.
• TUT1 anchors the U6 snRNA body, preventing dissociation during the oligo-uridylylation process.

Conclusions:

• TUT1 exhibits high specificity for U6 snRNA, utilizing its entire structure to ensure accurate oligo-uridylylation.
• The detailed structural insights explain the mechanism of U6 snRNA recognition and binding by TUT1, highlighting its role in splicing regulation.