Splicing factors PTBP1 and PTBP2 promote proliferation and migration of glioma cell lines.
Polypyrimidine tract-binding protein 1 (PTBP1) is a multi-functional RNA-binding protein that is aberrantly overexpressed in glioma. PTBP1 and its brain-specific homologue polypyrimidine tract-binding protein 2 (PTBP2) regulate neural precursor cell differentiation. However, the overlapping and non-overlapping target transcripts involved in this process are still unclear. To determine why PTBP1 and not PTBP2 would promote glial cell-derived tumours, both PTBP1 and PTBP2 were knocked down in the human glioma cell lines U251 and LN229 to determine the role of these proteins in cell proliferation, migration, and adhesion. Surprisingly, removal of both PTBP1 and PTBP2 slowed cell proliferation, with the double knockdown having no additive effects. Decreased expression of both proteins individually and in combination inhibited cell migration and increased adhesion of cells to fibronectin and vitronectin. A global survey of differential exon expression was performed following PTBP1 knockdown in U251 cells using the Affymetrix Exon Array to identify PTBP1-specific splicing targets that enhance gliomagenesis. In the PTBP1 knockdown, previously determined targets were unaltered in their splicing patterns. A single gene, RTN4 (Nogo) had significantly enhanced inclusion of exon 3 when PTBP1 was removed. Overexpression of the splice isoform containing exon 3 decreased cell proliferation to a similar degree as the removal of PTBP1. These results provide the first evidence that RNA-binding proteins affect the invasive and rapid growth characteristics of glioma cell lines. Its actions on proliferation appear to be mediated, in part, through alternative splicing of RTN4.
Cheung
Hannah C
HC
Department of Endocrine Neoplasia and Hormonal Disorders, University of Texas, M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Hai
Tao
T
Zhu
Wen
W
Baggerly
Keith A
KA
Tsavachidis
Spiridon
S
Krahe
Ralf
R
Cote
Gilbert J
GJ
D008841:Actin Cytoskeleton / Q000473:pathology; D017398:Alternative Splicing / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation; D005091:Exons / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques / Q000379:methods; D005910:Glioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D009185:Myelin Proteins / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D000070798:Nogo Proteins; D038941:Polypyrimidine Tract-Binding Protein / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured
D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009185:Myelin Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D000070798:Nogo Proteins; C450006:PTBP1 protein, human; C504334:PTBP2 protein, human; C000603199:RTN4 protein, human; D038941:Polypyrimidine Tract-Binding Protein