regulatory mechanisms for human thymidine kinase 2 and deoxyguanosine kinase
Sun, Ren
(2013).
Studies of enzymes in mitochondrial DNA precursor synthesis.
Diss. (sammanfattning/summary)
Uppsala :
Sveriges lantbruksuniv.,
Acta Universitatis Agriculturae Sueciae, 1652-6880
; 2013:64
ISBN 978-91-576-7866-9
eISBN 978-91-576-7867-6
[Doctoral thesis]
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Abstract
As important enzymes in mitochondrial nucleotide salvage pathway, thymidine kinase 2 (TK2) and deoxyguanosine kinase (dGK) are expressed constitutively in almost all cells. These two enzymes catalyze the initial rate-limiting phosphorylation of pyrimidine and purine deoxynucleosides, respectively, providing DNA precursors for mitochondrial DNA (mtDNA) replication.
Inherited genetic defects in TK2 have been associated with infantile myopathic form of mtDNA depletion syndrome (MDS). In study I, two mutations, R225W and a novel T230A, in TK2 are identified as a new genetic cause of adult-onset autosomal recessive progressive external ophthalmoplegia (arPEO) and the kinetic and structural effects of the two mutations on enzyme function have been characterized.
Nucleoside analogs are widely used in anti-viral and anti-cancer chemotherapy, but they can cause severe side-effect such as mtDNA depletion. In study II, the potential mechanism underlying pyrimidine nucleoside analogs-associated mitochondrial toxicities was investigated, and showed that thymidine analogs had opposite effects on dThd and dCyd phosphorylation and thus can inhibit dThd salvage, leading to imbalanced dTTP and dCTP pools. It was found that the mechanism is most likely due to that TK2 normally exists in an inactive form with bound dTTP.
The redox regulation of TK2 and dGK was studied in study III and IV. The activity of both enzymes was sensitive to the cellular redox status. Under oxidative stress, both TK2 and dGK can be reversibly S-glutathionylated by GSSG. The modification of the conserved Cys189 in TK2 was responsible for a partial inactivation and selective degradation of TK2 in mitochondria, most likely via the AAA⁺ Lon protease. The oxidative effect of nucleoside analogs was also evaluated. Treatment with 3’-azido- 2’,3’-dideoxythymidine (AZT) and 2’,3’-dideoxyinosine (ddI) led to degradation of mitochondrial TK2 and dGK, whereas uridine and guanosine supplementations to AZT respective ddI treatments prevented both proteins from degradation.
Authors/Creators: | Sun, Ren | ||||||||||||
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Title: | Studies of enzymes in mitochondrial DNA precursor synthesis | ||||||||||||
Subtitle: | regulatory mechanisms for human thymidine kinase 2 and deoxyguanosine kinase | ||||||||||||
Series/Journal: | Acta Universitatis Agriculturae Sueciae (1652-6880) | ||||||||||||
Year of publishing : | September 2013 | ||||||||||||
Number: | 2013:64 | ||||||||||||
Number of Pages: | 76 | ||||||||||||
Papers/manuscripts: |
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Place of Publication: | Uppsala | ||||||||||||
Publisher: | Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences | ||||||||||||
ISBN for printed version: | 978-91-576-7866-9 | ||||||||||||
ISBN for electronic version: | 978-91-576-7867-6 | ||||||||||||
ISSN: | 1652-6880 | ||||||||||||
Language: | English | ||||||||||||
Publication Type: | Doctoral thesis | ||||||||||||
Full Text Status: | Public | ||||||||||||
Agris subject categories.: | X Agricola extesions > X30 Life sciences | ||||||||||||
Subjects: | (A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Biochemistry and Molecular Biology | ||||||||||||
Agrovoc terms: | enzymes, thymidine, kinases, mitochondria, dna | ||||||||||||
Keywords: | Thymidine kinase 2, Deoxyguanosine kinase, Mitochondrial DNA, Progressive external ophthalmoplegia, Nucleoside analogs, AZT (3’-azido-2’,3’- dideoxythymidine), ddI (2’,3’-dideoxyinosine), S-glutathionylation | ||||||||||||
URN:NBN: | urn:nbn:se:slu:epsilon-e-1619 | ||||||||||||
Permanent URL: | http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-1619 | ||||||||||||
ID Code: | 10780 | ||||||||||||
Department: | (VH) > Dept. of Anatomy, Physiology and Biochemistry | ||||||||||||
Deposited By: | Mr Ren Sun | ||||||||||||
Deposited On: | 04 Sep 2013 12:30 | ||||||||||||
Metadata Last Modified: | 13 Dec 2014 23:52 |
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