LIN28 Zinc Knuckle Domain Is Required and Sufficient to Induce let-7 Oligouridylation

Cell Rep. 2017 Mar 14;18(11):2664-2675. doi: 10.1016/j.celrep.2017.02.044.

Abstract

LIN28 is an RNA binding protein that plays crucial roles in pluripotency, glucose metabolism, tissue regeneration, and tumorigenesis. LIN28 binds to the let-7 primary and precursor microRNAs through bipartite recognition and induces degradation of let-7 precursors (pre-let-7) by promoting oligouridylation by terminal uridylyltransferases (TUTases). Here, we report that the zinc knuckle domain (ZKD) of mouse LIN28 recruits TUT4 to initiate the oligouridylation of let-7 precursors. Our crystal structure of human LIN28 in complex with a fragment of pre-let-7f-1 determined to 2.0 Å resolution shows that the interaction between ZKD and RNA is constrained to a small cavity with a high druggability score. We demonstrate that the specific interaction between ZKD and pre-let-7 is necessary and sufficient to induce oligouridylation by recruiting the N-terminal fragment of TUT4 (NTUT4) and the formation of a stable ZKD:NTUT4:pre-let-7 ternary complex is crucial for the acquired processivity of TUT4.

Keywords: LIN28; LIN28A; RNA binding protein; RNA degradation; TUT4; TUTase; X-ray structure; Zcchc11; let-7; oligouridylation.

MeSH terms

  • Animals
  • Base Sequence
  • Gene Expression Regulation
  • Humans
  • Kinetics
  • Mice
  • MicroRNAs / metabolism*
  • Models, Molecular
  • Nucleic Acid Conformation
  • Protein Binding
  • Protein Domains
  • RNA-Binding Proteins / chemistry*
  • RNA-Binding Proteins / metabolism*
  • Recombinant Proteins / metabolism
  • Ribonuclease III / metabolism
  • Structure-Activity Relationship
  • Surface Plasmon Resonance
  • Uridine / metabolism*

Substances

  • Lin-28 protein, mouse
  • Lin28A protein, human
  • MicroRNAs
  • RNA-Binding Proteins
  • Recombinant Proteins
  • mirnlet7 microRNA, mouse
  • Ribonuclease III
  • Uridine