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An In Vitro Assay to Detect tRNA-Isopentenyl Transferase Activity
Published on: October 8, 2018
Hypomodification of transfer RNA in cancer with respect to queuosine
Chandramani Pathak1, Yogesh K Jaiswal, Manjula Vinayak
1School of Studies In Biochemistry, Jiwaji University, Gwalior, India.
Abstract:
Queuosine is a highly modified nucleoside analogue of guanosine. It is present only in the first position of anticodon loop of specific tRNA i.e., tRNA(his), tRNA(asp), tRNA(asn) and tRNA(tyr) and post transcriptionally modified with base-for-base exchange of guanine to queuine. The transfer RNA modifying enzyme transfer RNA guanine transglycosylase (TGTase) catalyzes the modification of tRNAs. Transfer RNA is completely modified with respect to queuosine in mature tissue, however modification is often incomplete in mitotically active cells. Hypomodification of transfer RNA is correlated with cell proliferation and malignancy. In the present study queuosine modification of transfer RNA and TGTase activity is compared in normal, Dalton's lymphoma ascites transplanted (DLAT) cancerous and queuine treated DLAT cancerous mouse liver. Transfer RNA of cancerous mouse is hypomodified in terms of queuosine modification. TGTase activity of cancerous mouse is found to decrease to less then half of enzyme activity of normal mouse; suggesting that the enzyme may be responsible for transfer RNA hypomodification. Exogenous treatment of queuine during development of cancer improves the queuosine modification of transfer RNA. The activators NaPP and ATP enhance TGTase activity of normal and DLAT cancerous mouse, where as 7mG inhibits the TGTase activity.
Insights
Queuosine modification in transfer RNA (tRNA) is often incomplete in cancerous cells, correlating with reduced transfer RNA guanine transglycosylase (TGTase) activity. Supplementing with queuine can restore tRNA modification, suggesting a therapeutic target for malignancy.
Area of Science:
- Molecular Biology
- Biochemistry
- Cancer Research
Background:
- Queuosine is a unique modified nucleoside found in specific transfer RNAs (tRNAs), essential for their function.
- Transfer RNA guanine transglycosylase (TGTase) is the enzyme responsible for queuosine modification.
- Hypomodification of tRNA with queuosine is observed in actively dividing cells and is linked to cancer.
Purpose of the Study:
- To investigate the role of queuosine modification and TGTase activity in cancer.
- To compare tRNA modification and TGTase activity in normal, cancerous, and queuine-treated cancerous mouse liver.
- To explore the potential of exogenous queuine as a therapeutic intervention.
Main Methods:
- Comparison of queuosine modification levels in tRNA from normal, Dalton's lymphoma ascites transplanted (DLAT) cancerous, and queuine-treated DLAT cancerous mouse liver.
- Assay of TGTase enzyme activity in the same experimental groups.
- Investigation of the effects of activators (NaPP, ATP) and inhibitor (7mG) on TGTase activity.
Main Results:
- Cancerous mouse liver exhibited hypomodified tRNA with significantly reduced TGTase activity compared to normal controls.
- Exogenous administration of queuine improved queuosine modification in the tRNA of cancerous mice.
- TGTase activity was enhanced by NaPP and ATP, while 7mG inhibited the enzyme in both normal and cancerous samples.
Conclusions:
- Reduced TGTase activity contributes to tRNA hypomodification in cancer.
- Restoration of queuosine modification via exogenous queuine shows promise for cancer therapy.
- TGTase activity can be modulated by specific activators and inhibitors, offering potential therapeutic targets.
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