Polypyrimidine tract binding protein modulates efficiency of polyadenylation
Polypyrimidine tract binding protein modulates efficiency of polyadenylation
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DOI：
10.1128/mcb.24.10.4174-4183.2004
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发表时间：
2004-05-01
影响因子：
5.3
通讯作者：
Proudfoot, N
中科院分区：
文献类型：
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作者：
Castelo-Branco, P;Furger, A;Proudfoot, N
多聚嘧啶区结合蛋白（PTB）是一种主要的核不均一核糖核蛋白，在mRNA代谢中具有多种作用，包括对可变剪接和内部核糖体进入位点驱动的翻译的调控。我们在此表明，PTB过表达4倍会导致由带有不同多聚腺苷酸化信号（pA信号）的转染基因构建体所产生的mRNA水平降低75%。这种效应是由于mRNA 3'端切割效率降低所致，并且体外分析显示PTB与CstF竞争识别pA信号富含嘧啶的下游序列元件。这可能与其在可变剪接中的作用类似，在可变剪接中PTB与U2AF竞争结合富含嘧啶的内含子序列。C2补体基因的pA信号不同寻常地具有一个依赖PTB的上游序列，因此通过RNA干扰降低PTB表达会减少C2 mRNA的表达，尽管PTB过表达仍然抑制多聚腺苷酸化。因此，我们表明PTB可通过其对mRNA 3'端加工的正负效应来充当mRNA表达的调节因子。
Polypyrimidine tract binding protein (PTB) is a major hnRNP protein with multiple roles in mRNA metabolism, including regulation of alternative splicing and internal ribosome entry site-driven translation. We show here that a fourfold overexpression of PTB results in a 75% reduction of mRNA levels produced from transfected gene constructs with different polyadenylation signals (pA signals). This effect is due to the reduced efficiency of mRNA 3' end cleavage, and in vitro analysis reveals that PTB competes with CstF for recognition of the pA signal's pyrimidine-rich downstream sequence element. This may be analogous to its role in alternative splicing, where PTB competes with U2AF for binding to pyrimidine-rich intronic sequences. The pA signal of the C2 complement gene unusually possesses a PTB-dependent upstream sequence, so that knockdown of PTB expression by RNA interference reduces C2 mRNA expression even though PTB overexpression still inhibits polyadenylation. Consequently, we show that PTB can act as a regulator of mRNA expression through both its negative and positive effects on mRNA 3' end processing.