Project description:Hairpin RNA (hpRNA) transgenes, with a perfect inverted-repeat (IR) DNA, have been the most successful RNA interference (RNAi) method in plants. Here we show that hpRNA transgenes were invariably methylated in the IR DNA and the adjacent promoter, causing transcriptional self-silencing and preventing the full potential of RNAi. Nucleotide substitutions in the sense sequence, which disrupts the perfect IR DNA structure, were sufficient to prevent the intrinsic DNA methylation resulting in more uniform and persistent RNAi. Substituting all cytosine (C) with thymine (T) nucleotides, in a G:U hpRNA design, prevented DNA methylation and self-silencing but still allowed for the formation of perfect hpRNA due to G:U wobble base-pairing. The G:U design induces effective RNAi in 90-96% of transgenic lines, compared to 57-65% for the traditional hpRNA design. Furthermore, while a traditional hpRNA transgene showed increasing DNA methylation and self-silencing from cotyledons to true leaves, the G:U transgenes avoided this developmental progression of self-silencing and induced RNAi throughout plant growth. The G:U and traditional hpRNA transgenes generated small interfering RNA (siRNA) with different 5’ phosphorylation, which resembled the endogenous tasiRNA and miRNA, respectively. Furthermore, our results suggest that siRNAs from the two transgene designs function differently to induce target DNA methylation, one (from traditional hpRNA) through the canonical RdDM pathway and the other (G:U hpRNA) a non-canonical pathway. Our study not only revealed a methylation-resistant RNAi transgene design but also provided new mechanistic insights into small RNA biogenesis and function in plants
Project description:Tiled regions surrounding 5 human genes as 36mers, HBG2, TIMP3, SYN3, FLNA, FBX07. The first three of these genes, we tiled with various mismatch oligos in addition to 'perfect match' oligos. Keywords: Mismatch hybridization experiment Tiled perfect match and various designs of mismatch oligonucleotide for several human genes. Goal was to observe the influence of various MM types on hybridization behavior in human, and compare it to yeast (see related slide).
Project description:Tiled regions surrounding 5 human genes as 36mers, HBG2, TIMP3, SYN3, FLNA, FBX07. The first three of these genes, we tiled with various mismatch oligos in addition to 'perfect match' oligos. Keywords: Mismatch hybridization experiment
Project description:Tiled 10kb region centered around ACT1 gene (YFL039C, CHROMOSOME 6 @ coords 48760-59195), double-stranded, 36mers at 1bp spacing, with mismatches and deletions; also tiled 6 genes of interest (YBL092W, YGR155W, YOL040C, YOR312C, YMR242C, YLR229C), coding strand only, 36mers at 1bp spacing, with some mismatches and deletions Keywords: Mismatch hybridization experiment Tiled perfect match and various designs of mismatch oligonucleotide for several yeast genes. Goal was to observe the influence of various MM types on hybridization behavior in yeast and compare it to human (see related slide).
Project description:The mismatch repair (MMR) family is a highly conserved group of proteins that function in correcting base-base and insertion-deletion mismatches generated during DNA replication. To systematically investigate the mismatch repair pathway, we conducted a proteomic analysis and identified MMR-associated protein complexes using a tandem-affinity purification coupled with mass spectrometry (TAP-MS) method. In total, we identified 262 high-confidence candidate interaction proteins (HCIPs).
Project description:Biases of DNA repair can shape the nucleotide landscape of genomes at evolutionary timescales. However, such biases have not yet been measured in chromatin for lack of technologies. Here we develop a genome-wide assay whereby the same DNA lesion is repaired in different chromatin contexts. We insert thousands of barcoded transposons carrying a reporter of DNA mismatch repair in the genome of mouse embryonic stem cells. Upon inducing a double-strand break between tandem repeats, a mismatch is generated when the single strand annealing repair pathway is used. Surprisingly, the mismatch repair machinery favors the same strand 60-80% of the time. The location of the lesion in the genome and the type of mismatch have little influence on the repair bias in this context.
Project description:Tiled 10kb region centered around ACT1 gene (YFL039C, CHROMOSOME 6 @ coords 48760-59195), double-stranded, 36mers at 1bp spacing, with mismatches and deletions; also tiled 6 genes of interest (YBL092W, YGR155W, YOL040C, YOR312C, YMR242C, YLR229C), coding strand only, 36mers at 1bp spacing, with some mismatches and deletions Keywords: Mismatch hybridization experiment
Project description:Background Mismatched oligonucleotides are widely used on microarrays to differentiate specific from nonspecific hybridization. While many experiments rely on such oligos, the hybridization behavior of various degrees of mismatch (MM) structure has not been extensively studied. Here, we present the results of two large-scale microarray experiments on S.cerevisiae and H.sapiens genomic DNA, to explore MM oligonucleotide behavior with real sample mixtures under tiling-array conditions. Results We examined all possible nucleotide substitutions at the central position of 36-nucleotide probes, and found that nonspecific binding by MM oligos depends upon the individual nucleotide substitutions they incorporate: C->A, C->G and T->A (yielding purine-purine mispairs) are most disruptive, whereas A->X were least disruptive. We also quantify a marked GC skew effect: substitutions raising probe GC content exhibit higher intensity (and vice versa). This skew is small in highly-expressed regions (±0.5% of total intensity range) and large (±2% or more) elsewhere. Multiple mismatches per oligo are largely additive in effect: each MM added in a distributed fashion causes an additional 21% intensity drop relative to PM, three-fold more disruptive than adding adjacent mispairs (7% drop per MM). This SuperSeries is composed of the following subset Series: GSE13172: Mismatch oligonucleotides in human GSE13174: Mismatch oligonucleotides in yeast Refer to individual Series