Regulation of expression of poly (A) binding protein in mammalian cells

控制mRNA的翻译和稳定性对于基因表达的调控是重要的，并在包括正常细胞生长和癌症在内的各种细胞过程中起着至关重要的作用。在信使核糖核酸的翻译过程中涉及到大量的因素。在多种翻译启动因子中，Poly(A)结合蛋白在mRNA翻译的启动中起着至关重要的作用。细胞质Poly(A)结合蛋白(PABP1)结合于真核基因的Poly(A)链。PABP1同时与5‘端结合的eIF4G和mRNA的Poly(A)链相互作用，并刺激mRNA的翻译。此外，PABP1被认为可以保护mRNAs免受降解。由于PABP1在mRNA代谢的几乎所有方面都发挥着重要作用，因此在多个水平上严格控制这一重要多肽的表达是至关重要的 我们实验室发表的结果表明，聚(A)结合蛋白(PABP)的表达在mRNA翻译水平上受到调控。PABP基因5‘端非翻译区含有两个翻译调控顺式元件。第一个是末端寡嘧啶束(TOP)，它在热休克处理后的细胞恢复过程中上调PABP mRNA的翻译。第二个控制元件位于上游，富含腺嘌呤残基。PABP在这个自我调节的顺式元件上与自己的mRNA结合，并阻止翻译。此外，我们还发现PABP是通过丝裂原激活的蛋白激酶-2(MKK-2)被磷酸化的。ERK1/2信号通路，而PABP通过破坏同源mRNA的稳定性来控制MKK-2的水平。在MKK-2基因的3‘非编码区，我们发现了一个62个核苷酸的长稳定控制元件(SCE)，它与PABP结合并形成一个异构体的RNA-蛋白质复合体，用于mRNA的衰变。我们的研究计划的目的是研究顶端元件和SCE元件在人类细胞中如何发挥作用的机制细节。为了实现这一点，我们将鉴定与这些控制元件相互作用的蛋白质，并研究这些蛋白质如何相互作用。

Control of mRNA translation and stability is important for the regulation of gene expression, and play crucial roles in a variety of cellular processes including normal cellular growth and cancer. A large number of factors are involved in the process of mRNA translation. Amongst the various translation initiation factors the poly (A) binding protein plays a crucial role in initiation of mRNA translation. The cytoplasmic poly (A) binding protein (PABP1) binding protein binds to the poly (A) tract of eukaryotic mRNA. PABP1 interacts with the 5 ' cap bound eIF4G and the poly (A) tract of mRNA simultaneously and stimulates mRNA translation. Furthermore, PABP1 is believed to protect mRNAs from degradation. Because of the important roles of PABP1 in almost all aspects of mRNA metabolism it is crucial that expression of this important polypeptide is tightly controlled at multiple levels Published results from our own laboratory have shown that expression of the poly (A)-binding protein (PABP) is regulated at the mRNA translation level. The 5 ' untranslated region of PABP mRNA contains two translational control cis elements. The first one is a terminal oligopyrimidine tract (TOP); it up regulates PABP mRNA translation during recovery of cells from heat shock treatment. The second control element is down stream from the TOP and is rich in adenine residues. PABP binds to its own mRNA at this auto regulatory cis element and prevents translation. In addition, we showed that PABP is phosphorylated through the mitogen activated protein kinase-kinase-2 (MKK-2) ? ERK1/2 signaling pathway, and PABP in turn controls the level of MKK-2 by destabilizing the cognate mRNA. At the 3 'UTR of the MKK-2 mRNA we have located the presence of a 62-nucleotide long stability control element (SCE) that binds PABP and forms a hetromeric RNA-protein complex for mRNA decay. The objective of our research proposal is to examine the mechanistic details of how the TOP and SCE elements function in human cells. To achieve this we will identify the proteins that interact with these control elements and also examine how these proteins interact with each other.