Human polypyrimidine tract-binding protein interacts with mitochondrial tRNA(Thr) in the cytosol

Nucleic Acids Res. 2016 Feb 18;44(3):1342-53. doi: 10.1093/nar/gkv1355. Epub 2015 Dec 10.


Human polypyrimidine tract-binding protein PTB is a multifunctional RNA-binding protein with four RNA recognition motifs (RRM1 to RRM4). PTB is a nucleocytoplasmic shuttle protein that functions as a key regulator of alternative pre-mRNA splicing in the nucleoplasm and promotes internal ribosome entry site-mediated translation initiation of viral and cellular mRNAs in the cytoplasm. Here, we demonstrate that PTB and its paralogs, nPTB and ROD1, specifically interact with mitochondrial (mt) tRNA(Thr) both in human and mouse cells. In vivo and in vitro RNA-binding experiments demonstrate that PTB forms a direct interaction with the T-loop and the D-stem-loop of mt tRNA(Thr) using its N-terminal RRM1 and RRM2 motifs. RNA sequencing and cell fractionation experiments show that PTB associates with correctly processed and internally modified, mature mt tRNA(Thr) in the cytoplasm outside of mitochondria. Consistent with this, PTB activity is not required for mt tRNA(Thr) biogenesis or for correct mitochondrial protein synthesis. PTB association with mt tRNA(Thr) is largely increased upon induction of apoptosis, arguing for a potential role of the mt tRNA(Thr)/PTB complex in apoptosis. Our results lend strong support to the recently emerging conception that human mt tRNAs can participate in novel cytoplasmic processes independent from mitochondrial protein synthesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs / genetics
  • Animals
  • Apoptosis / genetics
  • Base Sequence
  • Binding Sites / genetics
  • Cell Line
  • Cytoplasm / metabolism*
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Mice
  • Mitochondria / genetics
  • Molecular Sequence Data
  • NIH 3T3 Cells
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Nucleic Acid Conformation
  • Polypyrimidine Tract-Binding Protein / genetics
  • Polypyrimidine Tract-Binding Protein / metabolism*
  • Protein Binding
  • RNA Interference
  • RNA, Transfer, Thr / chemistry
  • RNA, Transfer, Thr / genetics
  • RNA, Transfer, Thr / metabolism*


  • Nerve Tissue Proteins
  • PTBP2 protein, human
  • PTBP3 protein, human
  • RNA, Transfer, Thr
  • Polypyrimidine Tract-Binding Protein