Structural and functional insights into human Tudor-SN, a key component linking RNA interference and editing

Area of Science:

• Molecular Biology
• Structural Biology
• RNA Biology

Background:

• Human Tudor-SN protein plays a role in microRNA precursor degradation.
• It links RNA interference and RNA editing pathways.
• Tudor-SN possesses staphylococcal nuclease-like (SN) domains (SN1-SN5), a tudor domain, and tandem SN repeats.

Purpose of the Study:

• To investigate the structural and functional roles of Tudor-SN's tandem SN domains.
• To elucidate the mechanism of RNA binding and cleavage by Tudor-SN.
• To understand the structural basis for substrate specificity.

Main Methods:

• Protein expression and purification of a truncated human Tudor-SN.
• X-ray crystallography to determine the 3D structure.
• Biochemical assays to assess RNA binding and cleavage activity.
• Molecular modeling studies.

Main Results:

• Tandem SN domains are essential for Tudor-SN's RNA binding and cleavage.
• The crystal structure reveals a crescent-shaped assembly of SN3, SN4, tudor, and SN5 domains.
• A basic surface on SN3 and SN4 domains is implicated in RNA binding.
• Citrate ions occupy putative RNase active sites.
• Modeling suggests a preference for cleaving RNA with multiple I.U wobble pairs.

Conclusions:

• Tandem SN domains in Tudor-SN function as a clamp for RNA substrate capture.
• The structural insights explain Tudor-SN's RNA binding and cleavage mechanism.
• Tudor-SN's structure facilitates its role in RNA processing and degradation.