Proteins Of Mismatch Repair System Research Articles

Abstract 170: Anticancer potential of curcuma and target identification in hematologic malignancies: A focus on mismatch repair

Abstract Introduction- Cancer, an heterogeneous condition, arises through mutations in the tumor suppressors and proto oncogenes which are otherwise involved in numerous cellular processes.These mutations rewire the signaling cascades to promote ‘malignant phenotype'. Under such circumstances the DNA repair system aids in rectifying the mutations and establishing normalcy.Plant derived products have shown promising success in treatment of cancer. In the present study, we make an attempt to screen various curcumin compounds to identify putative targets related to hematologic malignancies which in turn modulate the functionally altered mismatch repair system (MMR) using computational tools. Methods-A total of 536 curcumin compounds, retrieved from peer reviewed literature and black turmeric database, were analyzed for molecular characteristics, biological activities, ADME/Tox and, drug-like properties through Molinspiration and PreADMET. This was followed by prediction of site of metabolism via FAME3SOM tool. Simultaneously, COSMIC database was used for selection of proteins associated to haematologic malignancies. The database helped us to identify 9 proteins viz. abl1, max, myb, myc, pcna, p73, top3a, blm and vbp1; molecular aberrations of which are associated with malignant transformation in blood related cancers. Additionally, STRING identified these proteins having significant interaction with proteins of mismatch repair system. The crystal structures of the proteins were obtained from PDB and their domains and active sites were predicted using scanPROSITE, MOTIF Search, metaPOCKET2 and PrankWeb tools. Finally the proteins and ligands were energy minimized using YASARA and subjected to virtual screening and molecular docking using Autodock Vina and Autodock Tools respectively. Results-The overall results revealed six of the curcuma compounds (two monocarbonyl derivatives, one non-curcuminoid and three black turmeric natural compounds) may have the potential to modulate the identified targets and thus revive the MMR functionality; rescuing the genome from being unstable. Conclusion-With these analyses we predict that curcumin compounds can modulate therapeutic targets identified here and in turn rescue the function of MMR in hematologic malignancies. Citation Format: Priyanjali Bhattacharya, Trupti N. Patel. Anticancer potential of curcuma and target identification in hematologic malignancies: A focus on mismatch repair [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 170.

HGG-40. EXCEPTIONAL SYNCHRONOUS OCCURENCE OF A BRAF V600E MUTANT GLIOBLASTOMA AND A H3.3K27M MUTANT DIFFUSE INTRINSIC PONTINE GLIOMA: A CASE REPORT

We report herein the case of a 17-year-old female who presented with intracranial hypertension and diplopia. Magnetic resonance imaging showed a large left cystic and solid temporoparietal lesion, associated with an infiltrating lesion of the brainstem, hypointense in T1 and hyperintense in FLAIR sequences, without enhancement after injection of gadolinium. Complete resection of the parietal mass and biopsy of the brainstem lesion were performed. Histopathological analysis of the parietal mass showed glioblastoma (WHO grade IV) with no IDH1/2 or H3.3/H3.1 gene mutation detected by Sanger sequencing. Immunohistochemistry found the expression of the proteins of mismatch repair system. Whole exome and RNA sequencing identified a BRAF-V600E mutation. The brainstem lesion was a diffuse midline glioma, H3K27M-mutant (grade IV) according to the 2016 WHO classification. Pan-genomic SNP arrays of the 2 tumors showed distinct genetic alterations. The parietal glioblastoma displayed complex genomic alterations whereas the brainstem glioma harbored chromosome 7q gain, chromosome 9p and 10 losses, and RB, TP53 and CDKN2A homozygous deletions. The patient was treated by concomitant radiochemotherapy (according to Stupp protocol). After 12 cycles of temozolomide, there was complete remission persistant in the parietal lobe. The brainstem tumor was stable but progressed after 3 months of temozolomide discontinuation. Treatment with mTOR inhibitors was initiated. At 21-month follow-up, the patient remains with few symptoms. No predisposition syndrome was identified in the patient or her family. Concurrent glioblastomas with distinct driver gene mutations are exceptional.

Finding needles in a basestack: recognition of mismatched base pairs in DNA by small molecules

Mismatched (non-Watson-Crick) base pairs represent the most common type of DNA damage, as they are permanently formed in living cells due to erroneous insertion, deletion and misincorporation of bases. In vivo, they are readily recognised and repaired by the proteins of the DNA mismatch repair system, which identify the mismatch sites with high efficiency and fidelity. Notably, the last decades have witnessed the development of several chemically diverse families of small organic molecules and metal complexes that selectively bind to mismatched base pairs (and not to fully paired double-stranded DNA), much like the proteins of the mismatch repair system. This review focuses on these DNA mismatch-binding ligands, with an emphasis on their (often unusual) binding modes, as well as on the similarities and differences between the different classes of mismatch binders. Also discussed are the potential bioanalytical and therapeutic applications of mismatch-binding ligands.

In Vivo Visualization of Mismatch Repair in Bacillus Subtilis using Single-Molecule Fluorescence Microscopy

The high fidelity of DNA replication is vital to genomic integrity and ultimately to the survival of species. Errors occurring during DNA replication can have severe consequences such as producing certain types of cancers, and the correction of these errors is carried out by various DNA repair systems, one of which is the mismatch repair (MMR) system that exists in both prokaryotes and eukaryotes. Mismatched nucleotides are recognized by MutS, an MMR system protein that first binds to the mismatched DNA and then recruits other MMR proteins responsible for the downstream repair process. Despite its crucial role in this process, little is known about how MutS first locates mismatched base pairs. Two competing models have been proposed in the literature: the replisome-associated model argues that MutS is bound to and travels with the replication fork and can bind mismatches immediately as they are produced, while the scanning model states that MutS binds and scans the DNA strands on its own to search for mistakes long after the DNA polymerase complex has synthesized DNA. To address this question, we apply single-molecule fluorescence microscopy to reveal the in vivo distributions and dynamics of MutS and the replisome in live Bacillus subtilis bacterial cells. Based on photoactivated localization microscopy (PALM), PAmCherry-labeled MutS and mCitrine-labeled DnaX (a subunit of the replisome) are tracked with nanometer-scale precision to reveal the spatial relationship between these two as well as their motional correlations. Our preliminary results suggest transient yet significant co-localization between MutS-PAmCherry and DnaX-mCitrine and thus support the replisome-associated model.