TY - JOUR
T1 - Identification of Fhit as a post-transcriptional effector of Thymidine Kinase 1 expression
AU - Kiss, Daniel L.
AU - Waters, Catherine E.
AU - Ouda, Iman M.
AU - Saldivar, Joshua C.
AU - Karras, Jenna R.
AU - Amin, Zaynab A.
AU - Mahrous, Seham
AU - Druck, Teresa
AU - Bundschuh, Ralf A.
AU - Schoenberg, Daniel R.
AU - Huebner, Kay
N1 - Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/3/1
Y1 - 2017/3/1
N2 - FHIT is a genome caretaker gene that is silenced in > 50% of cancers. Loss of Fhit protein expression promotes accumulation of DNA damage, affects apoptosis and epithelial-mesenchymal transition, though molecular mechanisms underlying these alterations have not been fully elucidated. Initiation of genome instability directly follows Fhit loss and the associated reduced Thymidine Kinase 1 (TK1) protein expression. The effects on TK1 of Fhit knockdown and Fhit induction in the current study confirmed the role of Fhit in regulating TK1 expression. Changes in Fhit expression did not impact TK1 protein turnover or transcription from the TK1 promoter, nor steady-state levels of TK1 mRNA or turnover. Polysome profile analysis showed that up-regulated Fhit expression resulted in decreased TK1 RNA in non-translating messenger ribonucleoproteins and increased ribosome density on TK1 mRNA. Fhit does not bind RNA but its expression increased luciferase expression from a transgene bearing the TK1 5′-UTR. Fhit has been reported to act as a scavenger decapping enzyme, and a similar result with a mutant (H96) that binds but does not cleave nucleoside 5′,5′-triphosphates suggests the impact on TK1 translation is due to its ability to modulate the intracellular level of cap-like molecules. Consistent with this, cells expressing Fhit mutants with reduced activity toward cap-like dinucleotides exhibit DNA damage resulting from TK1 deficiency, whereas cells expressing wild-type Fhit or the H96N mutant do not. The results have implications for the mechanism by which Fhit regulates TK1 mRNA, and more broadly, for its modulation of multiple functions as tumor suppressor/genome caretaker.
AB - FHIT is a genome caretaker gene that is silenced in > 50% of cancers. Loss of Fhit protein expression promotes accumulation of DNA damage, affects apoptosis and epithelial-mesenchymal transition, though molecular mechanisms underlying these alterations have not been fully elucidated. Initiation of genome instability directly follows Fhit loss and the associated reduced Thymidine Kinase 1 (TK1) protein expression. The effects on TK1 of Fhit knockdown and Fhit induction in the current study confirmed the role of Fhit in regulating TK1 expression. Changes in Fhit expression did not impact TK1 protein turnover or transcription from the TK1 promoter, nor steady-state levels of TK1 mRNA or turnover. Polysome profile analysis showed that up-regulated Fhit expression resulted in decreased TK1 RNA in non-translating messenger ribonucleoproteins and increased ribosome density on TK1 mRNA. Fhit does not bind RNA but its expression increased luciferase expression from a transgene bearing the TK1 5′-UTR. Fhit has been reported to act as a scavenger decapping enzyme, and a similar result with a mutant (H96) that binds but does not cleave nucleoside 5′,5′-triphosphates suggests the impact on TK1 translation is due to its ability to modulate the intracellular level of cap-like molecules. Consistent with this, cells expressing Fhit mutants with reduced activity toward cap-like dinucleotides exhibit DNA damage resulting from TK1 deficiency, whereas cells expressing wild-type Fhit or the H96N mutant do not. The results have implications for the mechanism by which Fhit regulates TK1 mRNA, and more broadly, for its modulation of multiple functions as tumor suppressor/genome caretaker.
KW - 5′-UTR
KW - Fhit
KW - Thymidine kinase 1
KW - Translational control
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U2 - 10.1016/j.bbagrm.2017.01.005
DO - 10.1016/j.bbagrm.2017.01.005
M3 - Article
C2 - 28093273
AN - SCOPUS:85011112576
SN - 1874-9399
VL - 1860
SP - 374
EP - 382
JO - Biochimica et Biophysica Acta - Gene Regulatory Mechanisms
JF - Biochimica et Biophysica Acta - Gene Regulatory Mechanisms
IS - 3
ER -