RNA turnover plays a critical role in controlling the fate of mRNA in the cytoplasm. In mammalian cells, deadenylation is the major trigger of cytoplasmic mRNA degradation, yet little is known about the underlying mechanism and its regulation. In this proposal, we focus on the molecular and biochemical mechanisms for control of cytoplasmic deadenylation. A combined strategy will be exploited to dissect the mechanistic steps of mRNA turnover, including 1)""""""""epigenetic"""""""" approaches such as RNAi knock-down and dominant-negative effect by catalytic site mutants of poly(A) nuclease and other putative participating enzymes; 2) various methodologies for investigating protein-interactions; and 3) two transcriptional pulsing approaches for monitoring mRNA decay kinetics. We first concentrate on two cis-acting elements in the c-fos transcript, the AU-rich element and the major coding-region determinant, and their cognate binding proteins to learn how they mediate mRNA decay by triggering the initial rapid deadenylation step, and also to address the directionality of decay of the mRNA body. Poly(A) nucleases responsible for default/global (i.e., entire poly(A)* mRNA population) and cis-acting element-mediated deadenylation will be identified by systematic knock-down of different classes of poly(A) nuclease individually and in combination. Alterations of deadenylation in response to physiological changes will be evaluated as well. We hypothesize that the major cytoplasmic poly(A)-binding protein, PABP1, plays a key role in deadenylation and that association of poly(A) nuclease(s), either directly or indirectly, with the PABP1/poly(A) tail complex is a critical step in targeting the poly(A) tail of an mRNA for shortening. Our proposed experiments will help elucidate fundamental principles that govern selective and differential mRNA degradation in mammalian cells. ? ?
| Chen, Chyi-Ying A; Zhang, Yueqiang; Xiang, Yu et al. (2017) Antagonistic actions of two human Pan3 isoforms on global mRNA turnover. RNA 23:1404-1418 |
| Chen, Chyi-Ying A; Shyu, Ann-Bin (2017) Emerging Themes in Regulation of Global mRNA Turnover in cis. Trends Biochem Sci 42:16-27 |
| Masamha, Chioniso P; Xia, Zheng; Peart, Natoya et al. (2016) CFIm25 regulates glutaminase alternative terminal exon definition to modulate miR-23 function. RNA 22:830-8 |
| Chen, Chyi-Ying A; Chang, Jeffrey T; Ho, Yi-Fang et al. (2016) MiR-26 down-regulates TNF-?/NF-?B signalling and IL-6 expression by silencing HMGA1 and MALT1. Nucleic Acids Res 44:3772-87 |
| Yoshikawa, Takeshi; Wu, Jianfeng; Otsuka, Motoyuki et al. (2015) ROCK inhibition enhances microRNA function by promoting deadenylation of targeted mRNAs via increasing PAIP2 expression. Nucleic Acids Res 43:7577-89 |
| Shyu, Ann-Bin (2015) Study of mRNA turnover never decays. RNA 21:738-9 |
| Masamha, Chioniso P; Xia, Zheng; Yang, Jingxuan et al. (2014) CFIm25 links alternative polyadenylation to glioblastoma tumour suppression. Nature 510:412-6 |
| Chen, Chyi-Ying A; Shyu, Ann-Bin (2014) Emerging mechanisms of mRNP remodeling regulation. Wiley Interdiscip Rev RNA 5:713-22 |
| Chen, Chyi-Ying A; Shyu, Ann-Bin (2013) Protein segregase meddles in remodeling of mRNA-protein complexes. Genes Dev 27:980-4 |
| Chen, Chyi-Ying A; Shyu, Ann-Bin (2013) Deadenylation and P-bodies. Adv Exp Med Biol 768:183-95 |
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