Telomere integrity is important for mammalian cell survival and proliferation. Telomere attrition or exposed chromosomal ends could result in genome instability, DNA damage response, and ultimately cancer. Mutations in telomerase subunits or telomere regulators have been linked to premature aging and cancer. Understanding the cellular mechanisms of telomere maintenance may therefore help in developing therapies for diseases including cancer. The human 3'overhang binding protein POT1 helps to protect the telomere ssDNA and regulate telomerase access. Recently, the lab identified a new telomere associated protein TPP1/PTOP (also known as PIP1/TINT1). We found it to directly interact with POT1 and the telomerase. Furthermore, TPP1 forms the human telosome, along with POT1, TRF1, TRF2, RAP1, and TIN2. Our findings suggest that TPP1 controls telomere length by regulating telomere recruitment of POT1 and telomerase. The long-term goal is to study how dysregulation of telosome components may lead to telomere dysfunction and cancer development. The overall objective of this proposal is to understand the function of TPP1 in telomere protection and hematopoietic cancer. We hypothesize that TPP1 may heterodimerize with POT1 to protect telomere ends, and control telomerase access and activity.
Specific Aim 1. To determine the molecular mechanism of TPP1-mediated telomere end protection and length control. (1) The dynamic assembly, protein stability, and localization of the POT1-TPP1 complex in human cells will be investigated. We will determine protein modifications such as ubiquitination, and the cell cycle regulated localization and organization of the POT1-TPP1 complex. (2) The role of TPP1 in telomere end protection, cell survival, and cell cycle checkpoint activation will be determined through knockout, RNAi, and dominant negative expression.
Specific Aim 2 : To elucidate the role of TPP1 in controlling telomerase activity. How TPP1 interacts with the telomerase and controls telomerase activity, regulates cell cycle-dependent telomerase access to telomeres will be studied.
Specific Aim 3 : To investigate the consequences of telomere dysfunction in development and cancer. Chimeric mice whose hematopoietic systems are reconstituted with cells expressing dominant-negative TPP1 and TPP1 shRNA will be generated, and used to determine how TPP1 affects hematopoietic survival and development of hematopoietic cancers.
The studies described in this proposal should help to delineate the signaling mechanisms by which TPP1 regulates telomere maintenance in vivo, and provide insight into the regulation and mechanisms of TPP1 in development and telomere protection, especially during hematopoiesis. This work may provide a more refined picture about the complex signaling networks that are employed by the cells to control genome stability. Furthermore, valuable targets for mechanism-driven design of cancer and aging therapeutics may be identified through this project.
|Tang, Mengfan; Li, Yujing; Zhang, Yi et al. (2015) Disease mutant analysis identifies a new function of DAXX in telomerase regulation and telomere maintenance. J Cell Sci 128:331-41|
|Zhou, Ge; Wang, Jiping; Zhao, Mei et al. (2014) Gain-of-function mutant p53 promotes cell growth and cancer cell metabolism via inhibition of AMPK activation. Mol Cell 54:960-74|
|Li, Yujing; Fong, Ka-Wing; Tang, Mengfan et al. (2014) Fam118B, a newly identified component of Cajal bodies, is required for Cajal body formation, snRNP biogenesis and cell viability. J Cell Sci 127:2029-39|
|Liu, Yinyin; Kim, Hyeung; Liang, Jiancong et al. (2014) The death-inducer obliterator 1 (Dido1) gene regulates embryonic stem cell self-renewal. J Biol Chem 289:4778-86|
|Feng, Xuyang; Luo, Zhenhua; Jiang, Shuai et al. (2013) The telomere-associated homeobox-containing protein TAH1/HMBOX1 participates in telomere maintenance in ALT cells. J Cell Sci 126:3982-9|
|Han, Xin; Liu, Dan; Zhang, Yi et al. (2013) Akt regulates TPP1 homodimerization and telomere protection. Aging Cell 12:1091-9|
|Shi, Feng-Tao; Kim, Hyeung; Lu, Weisi et al. (2013) Ten-eleven translocation 1 (Tet1) is regulated by O-linked N-acetylglucosamine transferase (Ogt) for target gene repression in mouse embryonic stem cells. J Biol Chem 288:20776-84|
|Zhang, Yi; Chen, Liuh-Yow; Han, Xin et al. (2013) Phosphorylation of TPP1 regulates cell cycle-dependent telomerase recruitment. Proc Natl Acad Sci U S A 110:5457-62|
|Lu, Weisi; Zhang, Yi; Liu, Dan et al. (2013) Telomeres-structure, function, and regulation. Exp Cell Res 319:133-41|
|Fong, Ka-wing; Leung, Justin Wai-chung; Li, Yujing et al. (2013) MTR120/KIAA1383, a novel microtubule-associated protein, promotes microtubule stability and ensures cytokinesis. J Cell Sci 126:825-37|
Showing the most recent 10 out of 19 publications