Identification and characterization of novel ligase I inhibitors

Abstract

The terminal step of ligation of single and/or double-strand breaks during physiological processes such as DNA replication, repair and recombination requires participation of DNA ligases in all mammals. DNA Ligase I has been well characterised to play vital roles during these processes. Considering the indispensable role of DNA Ligase I, a therapeutic strategy to impede proliferation of cancer cells is by using specific small molecule inhibitors against it. In the present study, we have designed and chemically synthesised putative DNA Ligase I inhibitors. Based on various biochemical and biophysical screening approaches, we identify two prospective DNA Ligase I inhibitors, SCR17 and SCR21. Both the inhibitors blocked ligation of nicks on DNA in a concentration-dependent manner, when catalysed by cell-free extracts or purified Ligase I. Docking studies in conjunction with biolayer interferometry and gel shift assays revealed that both SCR17 and SCR21 can bind to Ligase I, particularly to the DNA Binding Domain of Ligase I with KD values in nanomolar range. The inhibitors did not show significant affinity towards DNA Ligase III and DNA Ligase IV. Further, addition of Ligase I could restore the joining, when the inhibitors were treated with testicular cell-free extracts. Ex vivo studies using multiple assays showed that even though cell death was limited in the presence of inhibitors in cancer cells, their proliferation was compromised. Hence, we identify two promising DNA Ligase I inhibitors, which can be used in biochemical and cellular assays, and could be further modified and optimised to target cancer cells. © 2016 Wiley Periodicals, Inc.

Aberrant DNA Double-strand Break Repair Threads in Breast Carcinoma: Orchestrating Genomic Insult Survival

“…Recently, researchers have attempted to block DSB repair proteins to retard carcinoma growth and proliferation. In line with inhibitor-based therapies, there are several reports on the development of the inhibitors SCR-7 and SCR-17, which are directed against DNA ligase IV and DNA ligase I in the NHEJ repair system 12,16. Reports on the phenotypic screening of drug inhibitors such as ARTIK-52, which is an androgen receptor inhibitor, show an enhanced replication-dependent DNA damage repair response and p53 activation in breast carcinoma cells 57.…”

“…Several inhibitors/drugs/silencing approaches are currently being used to target DNA DSB repair methods including HR and NHEJ in breast carcinoma and other cancer types 8,9,11–16. In this review, the authors attempted to summarize the efficacy of promising combinatorial therapies in breast carcinoma including chemo/radiotherapy combined with specific DNA DSB repair protein inhibitors.…”

Biochemical activity of RAGs is impeded by Dolutegravir, an HIV integrase inhibitor

“…High Precision Streptavidin Biosensor (SAX) sensors (Forte Bio, USA) were employed for studying the binding of RAG1 domains with or without Dolutegravir (analytes) to biotin tagged proteins (ligand) immobilised onto the (SSA) sensors as described previously 20,[43][44][45] using the Forte Bio OCTET Red 96 instrument. Before use, all the SAX sensor tips were hydrated in buffer (1X PBS) for 10 min.…”

Water-soluble SCR7 Can Abrogate DNA End Joining and Induce Cancer Cell Death

“…DNA ligases were overexpressed and purified from bacteria [14,30]. His-tagged Ligase IV/XRCC4 bicistronic vector (pMJ4052) was a kind gift from Dr. Mauro Modesti.…”