期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 277, 期 30, 页码 27200-27209出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M203887200
关键词
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The polypyrimidine tract-binding protein (PTB), an RNA-binding protein, is required for efficient translation of some mRNAs containing internal ribosomal entry sites (IRESs). Here we provide evidence that the addition of apoptosis-inducing agents to cells results in the cleavage of PTB isoforms 1, 2, and 4 by caspase-3. This cleavage of PTB separated the N-terminal region, containing NLS-RRM1, from the C-terminal region, containing RRM2-3-4. Our data indicate that there are three noncanonical caspase-3 target sites in PTBs, namely Ile-Val-Pro-Asp(7) down arrow Ile, Leu-Tyr-Thr-Asp(139) down arrow Ser, and Ala-Ala-Val-Asp(172) down arrow Ala. The C-terminal PTB fragments localized to the cytoplasm, as opposed to the nucleus where most intact PTBs are found. Moreover, these G terminal PTB fragments inhibited translation of polio-viral mRNA, which contains an IRES element requiring PTB for its activation. This suggests that translation of some IRES-containing mRNAs is regulated by proteolytic cleavage of PTB during apoptosis.
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