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Results for “Molecular Biology”

Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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At least 415 records · Page 23Linked to original sources
bioRxiv2017

Modulation of Genome Editing Outcomes by Cell Cycle Control of Cas9 Expression

Targeting specific chromosomal sequences for genome modification or regulation during particular phases of the cell cycle may prove useful in creating more precise, predictable genetic changes. Here, we present a system using a fusion protein comprised of a programmable DNA modification protein, Cas9, linked to a cell cycle regulated protein, geminin, as well as green fluorescent protein (GFP) for visualization. Despite the large size of Cas9 relative to geminin, cells were observed to express Cas9-GFP-geminin at levels which oscillate with the cell cycle. These fusion proteins are also shown to retain double-strand break (DSB) activity at specific chromosomal sequences to produce both indels and targeted integration of donor ssDNA. Most importantly, the ratio of ssDNA donor integration to non-homologous end joining (NHEJ) was observed to increase, suggesting that cell cycle control Cas9 expression may be an effective strategy to bias DNA repair outcomes.

molecular biology↗
bioRxiv2017

Autonomous Combinatorial Color Barcoding For Multiplexing Single Molecule RNA Visualization

Single molecular fluorescence in situ hybridization (smFISH) detects RNA transcripts with spatial information and digital molecular counting. However, the broad usage of smFISH is still hindered by the complex chemical probe conjugation or microscopy set-up, especially for investigating multiple gene expression. Here we present a multiple fluorophore enzymatic labeling method (termed HuluFISH) for smFISH probes to achieve flexible combinatorial color barcoding in single hybridization step. The multiplex capacity of HuluFISH follows an exponential growth with the increase of the number of fluorophore types. We demonstrate that this method can be used to detect cellular heterogeneity in embryonic mouse brain on single cell level.

molecular biology↗
bioRxiv2017

Autogenous Cross-Regulation Of Quaking mRNA Processing And Translation Balances Quaking Functions In Splicing And Translation

Quaking RNA binding protein (RBP) isoforms arise from a single Quaking gene, and bind the same RNA motif to regulate splicing, stability, decay, and localization of a large set of RNAs. However, the mechanisms by which the expression of this single gene is controlled to distribute appropriate amounts of each Quaking isoform to regulate such disparate gene expression processes are unknown. Here we explore the separate mechanisms that regulate expression of two isoforms, Quaking-5 (Qk5) and Quaking-6 (Qk6), in mouse muscle cells. We first demonstrate that Qk5 and Qk6 proteins have distinct functions in splicing and translation respectively, enforced primarily through differential subcellular localization. Using isoform-specific depletion, we find both Qk5 and Qk6 act through cis and trans post-transcriptional regulatory mechanisms on their own and each others transcripts, creating a network of auto- and cross-regulatory controls. Qk5 has a major role in nuclear RNA stability and splicing, whereas Qk6 acts through translational regulation. In different cell types the cross-regulatory influences discovered here generate a spectrum of Qk5/Qk6 ratios subject to additional cell type and developmental controls. These unexpectedly complex feedback loops underscore the importance of the balance of Qk isoforms, especially where they are key regulators of development and cancer.

molecular biology↗
bioRxiv2017

The LDB1 complex co-opts CTCF for erythroid lineage specific long-range enhancer interactions

Lineage-specific transcription factors are critical for long-range enhancer interactions but direct or indirect contributions of architectural proteins such as CTCF to enhancer function remain less clear. The LDB1 complex mediates enhancer-gene interactions at the {beta}-globin locus through LDB1 self-interaction. We find that a novel LDB1-bound enhancer upstream of carbonic anhydrase 2 (Car2) activates its expression by interacting directly with CTCF at the gene promoter. Both LDB1 and CTCF are required for enhancer-Car2 looping and the domain of LDB1 contacted by CTCF is necessary to rescue Car2 transcription in LDB1 deficient cells. Genome wide studies and CRISPR/Cas9 genome editing indicate that LDB1-CTCF enhancer looping underlies activation of a substantial fraction of erythroid genes. Our results provide a mechanism by which long-range interactions of architectural protein CTCF can be tailored to achieve a tissue-restricted pattern of chromatin loops and gene expression.

molecular biology↗
bioRxiv2017

Regulatory RNPs: A novel class of ribonucleoproteins that contribute to ribosome heterogeneity

Ribonucleoproteins (RNPs), which are comprised of non-coding RNA and associated proteins, are involved in essential cellular processes such as translation and pre-mRNA splicing. One class of RNP is the small Cajal body-specific RNP (scaRNP), which contributes to the biogenesis of small nuclear RNPs (snRNPs) that are central components of the spliceosome. Interestingly, three scaRNAs are internally processed, generating stable nucleolus-enriched RNAs of unknown function. Here we provide evidence that these RNAs become part of novel RNPs we term regulatory RNPs (regRNPs). We postulate that regRNPs can impact rRNA modifications via interactions with the guide RNA component of small nucleolar RNPs (snoRNPs). Most modifications within rRNA (predominantly pseudouridylation and ribose 2-O-methylation) are conducted by snoRNPs, and we hypothesize that the activity of at least some of these snoRNPs is under the control of regRNPs. Ribosome heterogeneity leading to specialized ribosomes is an exciting emerging concept. Because modifications within rRNA can vary in different physiological or pathological situations, rRNA modifications are thought to be the major source of ribosome heterogeneity. Our identification of regRNPs thus provides important and timely insight into how ribosome heterogeneity may be accomplished. This work also provides additional functional connections between the Cajal body and the nucleolus.\n\nSummary StatementProcessed scaRNAs give rise to a novel regulatory RNP which regulates the modification of ribosomal RNA. These findings provide insight into the mechanisms governing ribosome heterogeneity.

molecular biology↗
bioRxiv2017

Effects of the glucocorticoid drug prednisone on urinary proteome and candidate biomarkers

Urine is a good source of biomarkers for clinical proteomics studies. However, one challenge in the use of urine biomarkers is that outside factors can affect the urine proteome. Prednisone is a commonly prescribed glucocorticoid used to treat various diseases in the clinic. To evaluate the possible impact of glucocorticoid drugs on the urine proteome, specifically disease biomarkers, this study investigated the effects of prednisone on the rat urine proteome. Urine samples were collected from control rats and prednisone-treated rats after drug administration. The urinary proteome was analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and proteins were identified using label-free proteome quantification. Differentially expressed proteins and their human orthologs were analyzed with bioinformatics methods. A total of 523 urinary proteins were identified in rat urine. Using label-free quantification, 27 urinary proteins showed expression changes after prednisone treatment. A total of 16 proteins and/or their human orthologs have been previously annotated as disease biomarkers. After functional analysis, we found that the pharmacological effects of prednisone were reflected in the urine proteome. Thus, urinary proteomics has the potential to be a powerful drug efficacy monitoring tool in the clinic. Meanwhile, alteration of the urine proteome due to prednisone treatment should be considered in future disease biomarker studies.

molecular biology↗
bioRxiv2017

Improved DOP-PCR (iDOP-PCR): a robust and simple WGA method for efficient amplification of low copy number genomic DNA

Whole-genome amplification (WGA) techniques are used for non-specific amplification of low-copy number DNA, and especially for single-cell genome and transcriptome amplification. There are a number of WGA methods that have been developed over the years. One example is degenerate oligonucleotide-primed PCR (DOP-PCR), which is a very simple, fast and inexpensive WGA technique. Although DOP-PCR has been regarded as one of the pioneering methods for WGA, it only provides low genome coverage and a high allele dropout rate when compared to more modern techniques. Here we describe an improved DOP-PCR (iDOP-PCR). We have modified the classic DOP-PCR by using a new thermostable DNA polymerase (SD polymerase) with a strong strand-displacement activity and by adjustments in primers design. We compared iDOP-PCR, classic DOP-PCR and the well-established PicoPlex technique for whole genome amplification of both high- and low-copy number human genomic DNA. The amplified DNA libraries were evaluated by analysis of short tandem repeat genotypes and NGS data. In summary, iDOP-PCR provided a better quality of the amplified DNA libraries compared to the other WGA methods tested, especially when low amounts of genomic DNA were used as an input material.

molecular biology↗
bioRxiv2017

Supercoiling DNA locates mismatches

We present a method of detecting sequence defects by supercoiling DNA with magnetic tweezers. The method is sensitive to a single mismatched base pair in a DNA sequence of several thousand base pairs. We systematically compare DNA molecules with 0 to 16 adjacent mismatches at 1 M monovalent salt and 3.5 pN force and show that, under these conditions, a single plectoneme forms and is stably pinned at the defect. We use these measurements to estimate the energy and degree of end-loop kinking at defects. From this, we calculate the relative probability of plectoneme pinning at the mismatch under physiologically relevant conditions. Based on this estimate, we propose that DNA supercoiling could contribute to mismatch and damage sensing in vivo.

molecular biology↗
bioRxiv2017

Collection And Preservation Of Urinary Proteins Using A Fluff Pulp Diaper

Change is the most fundamental property of biomarker. Contrast to the blood, which is under homeostatic controls, urine reflects changes in the body earlier and more sensitive therefore is a better biomarker source. And drawing blood from infants and toddlers is hard and less tolerated. For patients limited by language, giving chief complaint is difficult. Thus, monitoring biomarkers in urine can provide valuable clues for diagnosis of diseases, especially pediatric diseases. Collecting urine from young children and some adult patients is more challenging than collecting it from healthy adults. Here, we propose a method that uses a fluff pulp diaper to collect urine. Urinary proteins were then eluted and adsorbed onto a piece of nitrocellulose membrane, which can be dried and stored in a vacuumed bag. SDS-PAGE and LC-MS/MS analysis indicated that this method is reproducible, and similar proteins were identified as those obtained using an acetone precipitation method. With this simple economical method, it is possible to collect and preserve urine samples from infants, toddlers, and patients with special needs, even for large-scale biomarker studies.

molecular biology↗
bioRxiv2017

Expression of short hairpin RNAs using the compact architecture of retroviral microRNA genes

Short hairpin RNAs (shRNAs) are effective in generating stable repression of gene expression. RNA polymerase III (RNAP III) type III promoters (U6 or H1) are typically used to drive shRNA expression. While useful for some knockdown applications, the robust expression of U6/H1-driven shRNAs can induce toxicity and generate heterogeneous small RNAs with undesirable off-target effects. Additionally, the U6 and H1 promoters encompass the majority of the [~]270 base pairs (bp) of vector space required for shRNA expression. This can limit the efficacy and/or number of delivery vector options, particularly when delivery of multiple gene/shRNA combinations is required. Here, we develop a compact shRNA (cshRNA) expression system based on retroviral microRNA (miRNA) gene architecture that uses RNAP III type II promoters. We demonstrate that cshRNAs coded from as little as 100 bps of total coding space can precisely generate small interfering RNAs (siRNAs) that are active in the RNA-induced silencing complex (RISC). We provide an algorithm with a user-friendly interface to design cshRNAs for desired target genes. This cshRNA expression system reduces the coding space required for shRNA expression by greater than two-fold as compared to the U6/H1 promoters, which may facilitate therapeutic RNAi applications where delivery vector space is limiting.

molecular biology↗
bioRxiv2017

Transcription Factors Orchestrate Dynamic Interplay Between Genome Topology And Gene Regulation During Cell Reprogramming

Chromosomal architecture is known to influence gene expression, yet its role in controlling cell fate remains poorly understood. Reprogramming of somatic cells into pluripotent stem cells by the transcription factors (TFs) Oct4, Sox2, Klf4 and Myc offers an opportunity to address this question but is severely limited by the low proportion of responding cells. We recently developed a highly efficient reprogramming protocol that synchronously converts somatic into pluripotent stem cells. Here, we employ this system to integrate time-resolved changes in genome topology with gene expression, TF binding and chromatin state dynamics. This revealed that TFs drive topological genome reorganization at multiple architectural levels, which often precedes changes in gene expression. Removal of locus-specific topological barriers can explain why pluripotency genes are activated sequentially, instead of simultaneously, during reprogramming. Taken together, our study implicates genome topology as an instructive force for implementing transcriptional programs and cell fate in mammals.

molecular biology↗
bioRxiv2017

Negative Correlation Between The Expression Of tlr4 And grp78 Is Characteristic Of Sepsis Onset And Progression

In sepsis caused by Gram-negative bacteria, modulation of Toll-like receptor 4 (TLR4) activity by modulators such as glucose-regulated protein 78 kDa (GRP78), is believed to shift the equilibrium between pro- and anti-inflammatory downstream signaling cascade. We measured daily mRNA tlr4 and grp78 expression levels in peripheral blood of a cohort of septic patients, upon intensive care admission, and modeled these mRNA values based on a sine damping function. We obtained negative correlations between tlr4 and grp78 mRNA in the survivor group. In contrast, such relation is lost in the deceased patients. Loss of homeostasis predicted by our model within the initial 5 days of hospitalization was confirmed by death of those patients up to 28 days later. Measuring the correlation patterns of the expression of these two genes serves as a robust means to gauge sepsis progression, requiring only three points of measurement on the first day of hospitalization.

molecular biology↗
bioRxiv2017

A Survey of Genome Editing Activity for 16 Cpf1 orthologs

The recently discovered class 2 CRISPR-Cas endonuclease Cpf1 offers several advantages over Cas9, including the ability to process its own array and requirement for just a single RNA guide. These attributes make Cpf1 promising for many genome engineering applications. To further expand the suite of Cpf1 tools available, we tested 16 Cpf1 orthologs for activity in eukaryotic cells. Four of these new enzymes demonstrated targeted activity, one of which, from Moraxella bovoculi AAX11_00205 (Mb3Cpf1), exhibited robust indel formation. We also show that Mb3Cpf1 displays some tolerance for a shortened PAM (TTN versus the canonical Cpf1 PAM TTTV). The addition of these enzymes to the genome editing toolbox will further expand the utility of this powerful technology.

molecular biology↗
bioRxiv2017

6S RNA Supports Recovery From Nitrogen Depletion In Synechocystis Sp. PCC 6803

BackgroundThe 6S RNA is a global transcriptional riboregulator, which is exceptionally widespread among most bacterial phyla. While its role is well-characterized in some heterotrophic bacteria, we subjected a cyanobacterial homolog to functional analysis, thereby extending the scope of 6S RNA action to the special challenges of photoautotrophic lifestyles.\n\nResultsPhysiological characterization of a 6S RNA deletion strain ({Delta}ssaA) demonstrates a delay in the recovery from nitrogen starvation. Significantly decelerated phycobilisome reassembly and glycogen degradation are accompanied with reduced photosynthetic activity compared to the wild type.\n\nTranscriptome profiling further revealed that predominantly genes encoding photosystem components, ATP synthase, phycobilisomes and ribosomal proteins were negatively affected in {Delta}ssaA. In vivo pull-down studies of the RNA polymerase complex indicated a promoting effect of 6S RNA on the recruitment of the cyanobacterial housekeeping {sigma} factor SigA, concurrently supporting dissociation of group 2 {sigma} factors during recovery from nitrogen starvation.\n\nConclusionsThis study reveals 6S RNA as an integral part of the cellular response of Synechocystis sp. PCC 6803 to changing nitrogen availability. According to these results, 6S RNA supports a rapid acclimation to changing nitrogen supply by regulating the switch from group 2 {sigma} factors SigB, SigC and SigE to SigA- dependent transcription.

molecular biology↗
bioRxiv2017

Ki-67 Contributes To Normal Cell Cycle Progression And Inactive X Heterochromatin In p21 Checkpoint-Proficient Human Cells

Ki-67 protein is widely used as a tumor proliferation marker. However, whether Ki-67 affects cell cycle progression has been controversial. Here, we demonstrate that depletion of Ki-67 in human hTERT-RPE1, WI-38, IMR90, hTERT-BJ cell lines and primary fibroblast cells slowed entry into S phase and coordinately downregulated genes related to DNA replication. Some gene expression changes were partially relieved in Ki-67-depleted hTERT-RPE1 cells by co-depletion of the Rb checkpoint protein, but more thorough suppression of the transcriptional and cell cycle defects was observed upon depletion of cell cycle inhibitor p21. Notably, induction of p21 upon depletion of Ki-67 was a consistent hallmark of cell types in which transcription and cell cycle distribution were sensitive to Ki-67; these responses were absent in cells that did not induce p21. Furthermore, upon Ki-67 depletion, a subset of inactive x (Xi) chromosomes in female hTERT-RPE1 cells displayed several features of compromised heterochromatin maintenance, including decreased H3K27me3 and H4K20me1 labeling. These chromatin alterations were limited to Xi chromosomes localized away from the nuclear lamina and were not observed in checkpoint-deficient 293T cells. Altogether, our results indicate that Ki-67 integrates normal S phase progression and Xi heterochromatin maintenance in p21 checkpoint-proficient human cells.

molecular biology↗
bioRxiv2017

Low-Cost HPV Screening And The Prevalence Of Cervical Infection In Asymptomatic Populations In Guatemala

BackgroundA low cost and accurate method for detecting high-risk (HR) HPV is important to permit HPV testing for cervical cancer prevention. We validated a low-cost commercially available HPV method (H13, Hybribio, Hong Kong) and determined the distribution of HPV infections in over 1717 cancer-free women in Guatemala.\n\nMethodsH13 results were compared with two more established HPV tests: (Xpert (Cepheid) and SPF10-LIPA25 (DDL)) in 40 mainly known positive specimens. HR-HPV was detected in cervical samples from 1717 cancer-free women receiving Pap smears using the Hybribio realtime PCR assay of 13 HR types. Selected HPV positive samples were sequenced to determine viral type.\n\nResultsThe Hybribio H13 Assay showed 93% identical results with Xpert, and 89% with SPF10-LIPA25. A total of 13% (226/1717) of women tested HPV+. The highest prevalence was found in younger women (<30 years, 22 %) and older ones ([&ge;]60 years, 15%). The six most common HR-HPV types among the 148 HPV+ typed were HPV16 (22%), HPV18 (11%), HPV39 (11%), HPV58 (10%), HPV52 (8%), and HPV45 (8%).\n\nConclusionsThe Hybribio Assay was low cost, and accurate in testing for HR-HPV infection. As in most places, HPV16 was the most prevalent HR type in Guatemala and the age-specific prevalence curve peaked in younger ages.\n\nHighlightsO_LIA low cost and accurate method, Hybribio Assay, could be used for CC testing in low income regions.\nC_LIO_LIA total of 13% of cancer-free women were HPV+ and positivity was associated with younger age (<30 years old) in Guatemala.\nC_LIO_LIHPV16 was the major prevalent type.\nC_LI

molecular biology↗
bioRxiv2017

Neuronal Inhibition Of The Autophagy Nucleation Complex Extends Lifespan In Post-Reproductive C. elegans

Autophagy is a ubiquitous catabolic process, which causes cellular bulk degradation of cytoplasmic components and thereby regulates cellular homeostasis. Inactivation of autophagy has been linked with detrimental effects to cells and organisms. The antagonistic pleiotropy theory postulates that fitness promoting genes during youth are harmful during aging (Williams 1957). On this basis we examined genes mediating post-reproductive longevity using an RNA interference screen. From this screen we identified 30 novel regulators of post-reproductive longevity including pha-4. Through downstream analysis of pha-4 we identify that genes governing the early stages of autophagy up until the stage of vesicle nucleation, such as bec-1, strongly extend both lifespan and healthspan. Further, our data demonstrates that the improvements in health and longevity are mediated through the neurons - resulting in reduced neurodegeneration and sarcopenia. We propose that autophagy switches from advantageous to harmful in the context of an age-associated dysfunction.

molecular biology↗