Small Molecules Blocking TONSL Histone Reader Domains
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Solution Overview
Problem
Current cancer treatments face challenges in effectively targeting and inhibiting the homologous recombination (HR) repair pathway, which is crucial for cancer cell survival and resistance to conventional chemotherapy, due to the lack of specific inhibitors for the TONSL protein and its complex with MMS22L.
Innovation Solution
The discovery of the TONSL Ankyrin Repeat Domain (ARD) as a histone reader specific for unmodified histone H4 tails provides a mechanism to target the HR repair pathway by developing small molecules that interfere with the binding of H4 tails to TONSL ARD, disrupting its function and impairing DNA repair processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional chemotherapy is used to treat cancer, then cancer cells are killed through DNA damage, but cancer cells develop resistance through enhanced HR repair pathway activation
Solution Approach 1:
The patent applies preliminary anti-action by developing TONSL inhibitors that preemptively block the HR repair pathway before cancer cells can activate it in response to chemotherapy-induced DNA damage. By inhibiting TONSL protein function upstream in the repair pathway, the patent prevents cancer cells from mounting their defensive repair response, thereby eliminating resistance mechanisms before they can develop.
2Reliability
If the HR repair pathway is inhibited to sensitize cancer cells to DNA damage, then treatment efficacy is improved, but normal cells that also rely on HR for DNA repair may be damaged
Solution Approach 1:
The patent applies local quality by designing TONSL inhibitors with selective action primarily in cancer cells. Cancer cells exhibit heightened dependence on the HR repair pathway due to their high proliferation rates and pre-existing DNA damage burden, making them locally more vulnerable to TONSL inhibition. Normal cells with lower DNA damage loads and slower division rates maintain sufficient repair capacity, creating a differential effect that spares healthy tissue while targeting cancer cells.
3Manufacturing precision
If small molecules are designed to specifically bind TONSL ARD domain to block histone H4 tail binding, then specific inhibition of TONSL-MMS22L complex is achieved, but the complexity of drug design and development increases
Solution Approach 1:
The patent applies the extraction principle by isolating and targeting the specific Ankyrin Repeat Domain (ARD) of TONSL that binds histone H4 tails. By focusing drug design on this discrete functional domain rather than the entire TONSL protein, the patent simplifies the molecular target while maintaining high specificity. The ARD domain serves as a self-contained binding interface that can be selectively inhibited by small molecules without affecting other TONSL functions or interacting proteins.
Solution Approach 2:
The patent uses the histone H4 tail binding interface as an intermediary target. Instead of designing molecules to directly inhibit TONSL's enzymatic or protein-protein interaction functions, the patent targets the H4 tail binding pocket in the ARD domain. This intermediary approach allows small molecules to compete with or disrupt the natural H4-TONSL interaction, providing a clear structural template for drug design based on the well-characterized histone-protein interface.
Data Source
AI summary
The present invention relates to small molecules interfering with the conformational space of the TONSL ARD occupied by the histone H4 tail. These small molecules targets the binding pocket of TONSL encompassing the H4 residues K12-R23 and act by preventing or disrupting the binding of the H4 tail K12-R23 with the TONSL ARD via direct competition or via allosteric disruption of the binding pocket.