ZBP1 recognition of beta-actin zipcode induces RNA looping

Area of Science:

• Molecular Biology
• RNA Metabolism
• Structural Biology

Background:

• Zipcode-binding protein 1 (ZBP1) regulates mRNA localization, stability, and translation.
• ZBP1 acts as a trans-acting factor for the beta-actin mRNA zipcode in the 3' UTR.
• ZBP1 is a multifunctional regulator of RNA metabolism impacting numerous mRNAs.

Purpose of the Study:

• To elucidate the molecular mechanism by which ZBP1 recognizes its RNA targets.
• To biochemically characterize the ZBP1-beta-actin zipcode interaction.
• To understand the structural basis of ZBP1 RNA recognition.

Main Methods:

• Biochemical characterization of ZBP1-RNA interaction.
• X-ray crystallography of human ortholog IMP1 KH34.
• Structural analysis of tandem KH domains.

Main Results:

• The third and fourth KH domains of ZBP1 specifically recognize a bipartite RNA element within the beta-actin zipcode.
• The structure of IMP1 KH34 reveals an anti-parallel pseudodimer conformation of tandem KH domains.
• ZBP1 binding induces RNA looping, enabling simultaneous contact by both KH domains.

Conclusions:

• ZBP1 utilizes its tandem KH domains to specifically recognize RNA targets through induced RNA looping.
• The structural arrangement of ZBP1's KH domains facilitates simultaneous binding to a bipartite RNA element.
• RNA looping induced by ZBP1 may promote the assembly of post-transcriptional regulatory complexes.