The control of mRNA stability is a critical determinant in the post-transcriptional regulation of eukaryotic gene expression. Even minor alterations in mRNA stability can have profound consequences and may manifest as clinical phenotypes as illustrated by the ability of aberrantly expressed proto-oncogenes that can give rise to malignancies. Despite the importance of mRNA stability in the control of gene expression, progress has only recently been made in the identification and characterization of the components that control mRNA turnover and their ultimate physiological consequence. We have focused our efforts on the study of nucleases involved in mRNA decay, in particular, mRNA 5'end decapping and the cell biological significance of decapping. We have now identified multiple confirmed and putative decapping enzymes, which appear to modulate a select subset of mRNAs and pathways. In this proposal we will expand on the cell biological and functional role of mRNA decapping enzymes. We have shown the Dcp2 decapping enzyme selectively modulates the decapping of mRNAs involved in innate immunity and will pursue its role in the innate immune response in Aim1. We have identified a novel class of decapping proteins represented by the mammalian DXO protein, which possesses an unusual intrinsic dual decapping and exonuclease activities. We have already shown DXO preferentially functions on incompletely capped pre-mRNAs in a nuclear pre-mRNA 5'end quality control mechanism, and now have evidence it also functions as a "canonical" decapping enzyme disproportionally modulating a subset of mRNAs involved in cytoskeletal architecture and cell migration. We will pursue the role of DXO in mRNA decapping and cell migration in Aim2.
In Aim3, we will build on our ongoing efforts to identify additional mRNA decapping enzymes and decipher the functional role of six new Nudix family proteins we recently demonstrated contain decapping activity in vitro, Nudt2, Nudt3, Nudt12, Nudt15, Nudt17 and Nudt19. We will initially focus on the evolutionarily conserved Nudt3 protein where preliminary data indicates it is a bona fide decapping enzyme in cells. Collectively, this work will provide novel insights into a fundamental post-transcriptional regulatory mechanism involved in gene expression and a framework for innovative approaches for therapeutic intervention in pathological conditions.

Public Health Relevance

Our overall objective is to understand the precise controls involved in mRNA turnover and to utilize this information to regulate gene expression under normal and disease states. Decapping is a key step in the ultimate demise of an mRNA and we will build on our ongoing functional studies delineating the novel role of decapping enzymes in cellular processes including innate immunity against pathogens and cell migration. This work will provide insight into a fundamental mechanism involved in the post-transcriptional control of gene expression and could provide a framework in novel approaches for therapeutic intervention.

National Institute of Health (NIH)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Bender, Michael T
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Rutgers University
Anatomy/Cell Biology
Schools of Arts and Sciences
New Brunswick
United States
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Tan, Dazhi; Zhou, Mi; Kiledjian, Megerditch et al. (2014) The ROQ domain of Roquin recognizes mRNA constitutive-decay element and double-stranded RNA. Nat Struct Mol Biol 21:679-85
Jurado, Ashley R; Tan, Dazhi; Jiao, Xinfu et al. (2014) Structure and function of pre-mRNA 5'-end capping quality control and 3'-end processing. Biochemistry 53:1882-98
Song, Man-Gen; Bail, Sophie; Kiledjian, Megerditch (2013) Multiple Nudix family proteins possess mRNA decapping activity. RNA 19:390-9
Jiao, Xinfu; Chang, Jeong Ho; Kilic, Turgay et al. (2013) A mammalian pre-mRNA 5' end capping quality control mechanism and an unexpected link of capping to pre-mRNA processing. Mol Cell 50:104-15
Li, You; Dai, Jihong; Song, Mangen et al. (2012) Dcp2 decapping protein modulates mRNA stability of the critical interferon regulatory factor (IRF) IRF-7. Mol Cell Biol 32:1164-72
Li, You; Song, Mangen; Kiledjian, Megerditch (2011) Differential utilization of decapping enzymes in mammalian mRNA decay pathways. RNA 17:419-28
Jiao, Xinfu; Xiang, Song; Oh, Chanseok et al. (2010) Identification of a quality-control mechanism for mRNA 5'-end capping. Nature 467:608-11
Song, Man-Gen; Li, You; Kiledjian, Megerditch (2010) Multiple mRNA decapping enzymes in mammalian cells. Mol Cell 40:423-32
Bail, Sophie; Swerdel, Mavis; Liu, Hudan et al. (2010) Differential regulation of microRNA stability. RNA 16:1032-9
Jiao, Xinfu; Chen, Hongxin; Chen, Jianmin et al. (2009) Modulation of neuritogenesis by a protein implicated in X-linked mental retardation. J Neurosci 29:12419-27

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