Lodhi, N. | Search bioRxiv

bioRxiv2021

Epigenetic Malleability at Core Promoter Regulates Tobacco PR-1a Expression after Salicylic Acid Treatment

O_LITobaccos PR-1a gene is induced by pathogen attack or exogenous application of Salicylic Acid (SA). However, the epigenetic modifications of the most important inducible promoter of the PR-1a gene are not understood clearly. C_LIO_LINucelosome mapping and chromatin immunoprecipitation assay were used to define the histone modification on the PR-1a promoter. C_LIO_LIHere, we report the epigenetic modifications over core promoter lead to disassembly of nucleosome (spans from -102 to +55 bp,masks TATA and transcription initiation) and repressor complex in induced state. ChIP assays demonstrate repressive chromatin of dimethylation at H3K9 and H4K20 of core promoter maintain uninduced state. While, active chromatin marks di and trimethylation of H3K4, acetylation of H3K9 and H4K16 are increased and lead the induction of PR-1a following SA treatment. TSA enhances expression of PR-1a by facilitating the histone acetylation, however increased expression of negative regulator (SNI1) of AtPR1, suppresses its expression in Arabidopsis thalianas mutants. C_LIO_LIConstitutive expression of AtPR1 in Histone Acetyl Transferases (HATs), LSD1, and SNI1 suggests that its inactive state is indeed maintained by a repressive complex and this strict regulation of pathogenesis related genes is conserved across species. C_LI SUMMARYHistone methylation and acetylation regulation of tobacco PR-1a promoter are significant for disassembly of the nucleosome and repressor proteins during induction.

plant biology↗

bioRxiv2021

Combination of High Dose Rate Radiations (10X FFF/2400 MU/min/10 MV X-rays) and Paclitaxel Selectively Eliminates Melanoma Cells

PurposeMelanoma is one of the most aggressive cancer with 1.6% of total cancer deaths in United States. In recent years treatment options for metastatic melanoma have been improved by the FDA approval of new therapeutic agents. However, these inhibitors based therapies are non-specific and have severe toxicities including hyperkeratosis, photosensitivity, hepatitis, arthralgia and fatigue. The aim of this study is to determine the synthetic lethal effect (paclitaxel and radiations) on melanoma cells and reduce the total radiation doses by increasing the dose rates up to 2400 MU/min. MethodsWe previously reported a radiation treatment (10 MV x-rays, 10X-FFF, dose rate 2400MU/min, low total dose 0.5 Gy) that kills melanoma cells with 80% survival of normal HEM in vitro. In this study we extended the radiation cycle up to four and include paclitaxel treatment to study the synthetic lethal effect on melanoma and two additional normal primary cells, HDF and HEK. Cells were treated with paclitaxel prior to radiations of dose rate of 400 and 2400 MU/min with total radiation dose of only 0.5 Gy. To study induction of apoptosis and cell death, mitochondria respiration assay, DNA damage assay and colony formation assay were performed. ResultsFour days of consequent radiation treatment with paclitaxel significantly reduces the survival of melanoma cells by inducing of apoptosis and mitochondrial damages. After treatment, excessive DNA damage in melanoma cells leads to increase in expression of pro-apoptotic genes (Casp3) and decrease in expression of DNA repair gene (PARP1) and anti-apoptotic gene (Bcl2) to activate apoptosis pathway. Combination of paclitaxel and radiations reduces the survival of melanoma cells colonies when compared to radiation alone. ConclusionOur study indicates radiations with paclitaxel has potential synthetic lethal effect on melanoma cells and can be develop as therapy for melanoma without having toxicities or harmful effects to normal primary skin cells.

cancer biology↗