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Thr729 in human topoisomerase I modulates anti-cancer drug resistance by altering protein domain communications as suggested by molecular dynamics simulations.

Chillemi G, D'Annessa I, Fiorani P, Losasso C, Benedetti P, Desideri A - Nucleic Acids Res. (2008)

Bottom Line: Both mutants can bind to the DNA substrate and are enzymatically active, but while Thr729Lys is resistant even at high concentration of the camptothecin (CPT) anti-cancer drug, Thr729Pro shows only a mild reduction in drug sensitivity and in DNA binding.MD simulations show that the Thr729Lys mutation provokes a structural perturbation of the CPT-binding pocket.The simulations also show the complete abolishment, in the Thr729Lys mutant, of the protein communications between the C-terminal domain (where the active Tyr723 is located) and the linker domain, that plays an essential role in the control of the DNA rotation, thus explaining the distributive mode of action displayed by this mutant.

View Article: PubMed Central - PubMed

Affiliation: CASPUR Inter-University Consortium for the Application of Super-Computing for Universities and Research, Via dei Tizii 6, Rome 00185, Italy. g.chillemi@caspur.it

ABSTRACT
The role of Thr729 in modulating the enzymatic function of human topoisomerase I has been characterized by molecular dynamics (MD) simulation. In detail, the structural-dynamical behaviour of the Thr729Lys and the Thr729Pro mutants have been characterized because of their in vivo and in vitro functional properties evidenced in the accompanying paper. Both mutants can bind to the DNA substrate and are enzymatically active, but while Thr729Lys is resistant even at high concentration of the camptothecin (CPT) anti-cancer drug, Thr729Pro shows only a mild reduction in drug sensitivity and in DNA binding. MD simulations show that the Thr729Lys mutation provokes a structural perturbation of the CPT-binding pocket. On the other hand, the Thr729Pro mutant maintains the wild-type structural scaffold, only increasing its rigidity. The simulations also show the complete abolishment, in the Thr729Lys mutant, of the protein communications between the C-terminal domain (where the active Tyr723 is located) and the linker domain, that plays an essential role in the control of the DNA rotation, thus explaining the distributive mode of action displayed by this mutant.

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Average per-residue RMSF represented as a function of the residue number for the wild-type hTop1p protein (black line), Tyr729Lys mutant (red line) and Tyr729Pro mutant (green line).
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Figure 1: Average per-residue RMSF represented as a function of the residue number for the wild-type hTop1p protein (black line), Tyr729Lys mutant (red line) and Tyr729Pro mutant (green line).

Mentions: The per residue RMSF analysis (Figure 1) indicates that the linker domain of the Thr729Pro mutant is less fluctuating (green line in Figure 1) when compared to the wild protein and the Thr729Lys mutant (black and red lines, respectively). Figure 1 also shows differences for the residues 601–615 fluctuations (in the C-terminal region of the core domain), being very high, intermediate and low for the Thr729Lys mutant, wild-type and Thr729Pro mutant simulations, respectively. Actually, the whole C-terminal region of the core domain, the linker and the C-terminal domain are less mobile in the Thr729Pro system, as compared to the other two systems.Figure 1.


Thr729 in human topoisomerase I modulates anti-cancer drug resistance by altering protein domain communications as suggested by molecular dynamics simulations.

Chillemi G, D'Annessa I, Fiorani P, Losasso C, Benedetti P, Desideri A - Nucleic Acids Res. (2008)

Average per-residue RMSF represented as a function of the residue number for the wild-type hTop1p protein (black line), Tyr729Lys mutant (red line) and Tyr729Pro mutant (green line).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2553568&req=5

Figure 1: Average per-residue RMSF represented as a function of the residue number for the wild-type hTop1p protein (black line), Tyr729Lys mutant (red line) and Tyr729Pro mutant (green line).
Mentions: The per residue RMSF analysis (Figure 1) indicates that the linker domain of the Thr729Pro mutant is less fluctuating (green line in Figure 1) when compared to the wild protein and the Thr729Lys mutant (black and red lines, respectively). Figure 1 also shows differences for the residues 601–615 fluctuations (in the C-terminal region of the core domain), being very high, intermediate and low for the Thr729Lys mutant, wild-type and Thr729Pro mutant simulations, respectively. Actually, the whole C-terminal region of the core domain, the linker and the C-terminal domain are less mobile in the Thr729Pro system, as compared to the other two systems.Figure 1.

Bottom Line: Both mutants can bind to the DNA substrate and are enzymatically active, but while Thr729Lys is resistant even at high concentration of the camptothecin (CPT) anti-cancer drug, Thr729Pro shows only a mild reduction in drug sensitivity and in DNA binding.MD simulations show that the Thr729Lys mutation provokes a structural perturbation of the CPT-binding pocket.The simulations also show the complete abolishment, in the Thr729Lys mutant, of the protein communications between the C-terminal domain (where the active Tyr723 is located) and the linker domain, that plays an essential role in the control of the DNA rotation, thus explaining the distributive mode of action displayed by this mutant.

View Article: PubMed Central - PubMed

Affiliation: CASPUR Inter-University Consortium for the Application of Super-Computing for Universities and Research, Via dei Tizii 6, Rome 00185, Italy. g.chillemi@caspur.it

ABSTRACT
The role of Thr729 in modulating the enzymatic function of human topoisomerase I has been characterized by molecular dynamics (MD) simulation. In detail, the structural-dynamical behaviour of the Thr729Lys and the Thr729Pro mutants have been characterized because of their in vivo and in vitro functional properties evidenced in the accompanying paper. Both mutants can bind to the DNA substrate and are enzymatically active, but while Thr729Lys is resistant even at high concentration of the camptothecin (CPT) anti-cancer drug, Thr729Pro shows only a mild reduction in drug sensitivity and in DNA binding. MD simulations show that the Thr729Lys mutation provokes a structural perturbation of the CPT-binding pocket. On the other hand, the Thr729Pro mutant maintains the wild-type structural scaffold, only increasing its rigidity. The simulations also show the complete abolishment, in the Thr729Lys mutant, of the protein communications between the C-terminal domain (where the active Tyr723 is located) and the linker domain, that plays an essential role in the control of the DNA rotation, thus explaining the distributive mode of action displayed by this mutant.

Show MeSH
Related in: MedlinePlus