Expanding the Zebrafish Genetic Code through Site-Specific Introduction of Azido-lysine, Bicyclononyne-lysine, and Diazirine-lysine.

Site-specific incorporation of un-natural amino acids (UNAA) is a powerful approach to engineer and understand protein function. Site-specific incorporation of UNAAs is achieved through repurposing the amber codon (UAG) as a sense codon for the UNAA, using a tRNACUA that base pairs with an UAG codon in the mRNA and an orthogonal amino-acyl tRNA synthetase (aaRS) that charges the tRNACUA with the UNAA. Here, we report an expansion of the zebrafish genetic code to incorporate the UNAAs, azido-lysine (AzK), bicyclononyne-lysine (BCNK), and diazirine-lysine (AbK) into green fluorescent protein (GFP) and glutathione-s-transferase (GST). We also present proteomic evidence for UNAA incorporation into GFP. Our work sets the stage for the use of AzK, BCNK, and AbK introduction into proteins as a means to investigate and engineer their function in zebrafish.

Deciphering the genomic targets of alkylating polyamide conjugates using high-throughput sequencing.

Chemically engineered small molecules targeting specific genomic sequences play an important role in drug development research. Pyrrole-imidazole polyamides (PIPs) are a group of molecules that can bind to the DNA minor-groove and can be engineered to target specific sequences. Their biological effects rely primarily on their selective DNA binding. However, the binding mechanism of PIPs at the chromatinized genome level is poorly understood. Herein, we report a method using high-throughput sequencing to identify the DNA-alkylating sites of PIP-indole-seco-CBI conjugates. High-throughput sequencing analysis of conjugate 2: showed highly similar DNA-alkylating sites on synthetic oligos (histone-free DNA) and on human genomes (chromatinized DNA context). To our knowledge, this is the first report identifying alkylation sites across genomic DNA by alkylating PIP conjugates using high-throughput sequencing.

Genome-Wide Assessment of the Binding Effects of Artificial Transcriptional Activators by High-Throughput Sequencing.

One of the major goals in DNA-based personalized medicine is the development of sequence-specific small molecules to target the genome. SAHA-PIPs belong to such class of small molecule. In the context of the complex eukaryotic genome, the differential biological effects of SAHA-PIPs are unclear. This question can be addressed by identifying the binding regions across the genome; however, it is a challenge to enrich small-molecule-bound DNA without chemical crosslinking. Here, we developed a method that employs high-throughput sequencing to map the binding area of small molecules throughout the chromatinized human genome. Analysis of the sequenced data confirmed the presence of specific binding sites for SAHA-PIPs from the enriched sequence reads. Mapping the binding sites and enriched regions on the human genome clarifies the reason for the distinct biological effects of SAHA-PIP. This approach will be useful for identifying the function of other small molecules on a large scale.

Effect of ATRX and G-Quadruplex Formation by the VNTR Sequence on α-Globin Gene Expression.

ATR-X (α-thalassemia/mental retardation X-linked) syndrome is caused by mutations in chromatin remodeler ATRX. ATRX can bind the variable number of tandem repeats (VNTR) sequence in the promoter region of the α-globin gene cluster. The VNTR sequence, which contains the potential G-quadruplex-forming sequence CGC(GGGGCGGGG)n , is involved in the downregulation of α-globin expression. We investigated G-quadruplex and i-motif formation in single-stranded DNA and long double-stranded DNA. The promoter region without the VNTR sequence showed approximately twofold higher luciferase activity than the promoter region harboring the VNTR sequence. G-quadruplex stabilizers hemin and TMPyP4 reduced the luciferase activity, whereas expression of ATRX led to a recovery in reporter activity. Our results demonstrate that stable G-quadruplex formation by the VNTR sequence downregulates the expression of α-globin genes and that ATRX might bind to and resolve the G-quadruplex.

A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts.

Small molecules capable of modulating epigenetic signatures can activate the transcription of tissue-restricted genes in a totally unrelated cell type and have potential use in epigenetic therapy. To provide an example for an initial approach, we report here on one synthetic small-molecule compound-termed "SAHA-PIP X"-from our library of conjugates. This compound triggered histone acetylation accompanied by the transcription of retinal-tissue-related genes in human dermal fibroblasts (HDFs).

DEcancer: Machine learning framework tailored to liquid biopsy based cancer detection and biomarker signature selection.

Cancer is a leading cause of mortality worldwide. Over 50% of cancers are diagnosed late, rendering many treatments ineffective. Existing liquid biopsy studies demonstrate a minimally invasive and inexpensive approach for disease detection but lack parsimonious biomarker selection, exhibit poor cancer detection performance and lack appropriate validation and testing. We established a tailored machine learning pipeline, DEcancer, for liquid biopsy analysis that addresses these limitations and improved performance. In a test set from a published cohort of 1,005 patients including 8 cancer types and 812 cancer-free individuals, DEcancer increased stage 1 cancer detection sensitivity across cancer types from 48 to 90%. In addition, with a test set cohort of patients from a high dimensional proteomics dataset of 61 lung cancer patients and 80 cancer-free individuals, DEcancer's performance using a 14-43 protein panel was comparable to 1,000 original proteins. DEcancer is a promising tool which may facilitate improved cancer detection and management.

SPRTN protease-cleaved MRE11 decreases DNA repair and radiosensitises cancer cells.

The human MRE11/RAD50/NBS1 (MRN) complex plays a crucial role in sensing and repairing DNA DSB. MRE11 possesses dual 3'-5' exonuclease and endonuclease activity and forms the core of the multifunctional MRN complex. We previously identified a C-terminally truncated form of MRE11 (TR-MRE11) associated with post-translational MRE11 degradation. Here we identified SPRTN as the essential protease for the formation of TR-MRE11 and characterised the role of this MRE11 form in its DNA damage response (DDR). Using tandem mass spectrometry and site-directed mutagenesis, the SPRTN-dependent cleavage site for MRE11 was identified between 559 and 580 amino acids. Despite the intact interaction of TR-MRE11 with its constitutive core complex proteins RAD50 and NBS1, both nuclease activities of truncated MRE11 were dramatically reduced due to its deficient binding to DNA. Furthermore, lack of the MRE11 C-terminal decreased HR repair efficiency, very likely due to abolished recruitment of TR-MRE11 to the sites of DNA damage, which consequently led to increased cellular radiosensitivity. The presence of this DNA repair-defective TR-MRE11 could explain our previous finding that the high MRE11 protein expression by immunohistochemistry correlates with improved survival following radical radiotherapy in bladder cancer patients.

RNA-DNA Triplex Formation by Long Noncoding RNAs.

Long noncoding RNAs (lncRNAs) play a pivotal role in the regulation of biological processes through various mechanisms that are not fully understood. Proposed mechanisms include regulation based on RNA-protein interactions, as well as RNA-RNA interactions and RNA-DNA interactions. Here, we focus on one possible mechanism that lncRNA might be using to impact biological function, the RNA-DNA triplex formation. We summarize currently available examples of lncRNA triplex formation and discuss the details surrounding orientation of triplex formation as one of the key properties guiding this process. We propose that symmetrical triplex-forming motifs, especially those in cis-acting lncRNAs, favor triplex formation. We also consider the effects of lncRNA structures, protein or ligand binding, and chromatin structures on the lncRNAs triplex formation.

Identification of a small molecule that turns ON the pluripotency gene circuitry in human fibroblasts.

A nontransgenic approach to reprogram mouse somatic cells into induced pluripotent stem cells using only small molecules got achieved to propose a potential clinical-friendly cellular reprogramming strategy. Consequently, the screening and identification of small molecules capable of inducing pluripotency genes in human cells are increasingly a focus of research. Because cellular reprogramming is multifactorial in nature, there is a need for versatile small molecules capable of modulating the complicated gene networks associated with pluripotency. We have developed a targeting small molecule called SAHA-PIP comprising the histone deacetylase inhibitor SAHA and the sequence-specific DNA binding pyrrole-imidazole polyamides for modulating distinct gene networks. Here, we report the identification of a SAHA-PIP termed Ì that could trigger genome-wide epigenetic reprogramming and turn ON the typically conserved core pluripotency gene network. Through independent lines of evidence, we report for the first time a synthetic small molecule inducer that target and activate the OCT-3/4 regulated pluripotency genes in human dermal fibroblasts.

Targeted suppression of EVI1 oncogene expression by sequence-specific pyrrole-imidazole polyamide.

Human ectopic viral integration site 1 (EVI1) is an oncogenic transcription factor known to play a critical role in many aggressive forms of cancer. Its selective modulation is thought to alter the cancer-specific gene regulatory networks. Pyrrole-imidazole polyamides (PIPs) are a class of small DNA binders that can be designed to target any destined DNA sequence. Herein, we report a sequence-specific pyrrole-imidazole polyamide, PIP1, which can target specific base pairs of the REL/ELK1 binding site in the EVI1 minimal promoter. The designed PIP1 significantly inhibited EVI1 in MDA-MB-231 cells. Whole-transcriptome analysis confirmed that PIP1 affected a fraction of EVI1-mediated gene regulation. In vitro assays suggested that this polyamide can also effectively inhibit breast cancer cell migration. Taken together, these results suggest that EVI1-targeted PIP1 is an effective transcriptional regulator in cancer cells.