Project description:Severe loss-of-function alleles of DCL1 are embryonic lethal. Defects in cell division were seen as early as the globular stage in the strong loss-of-function allele dcl1-15. Phenotypic work with dcl1-15 and the null allele dcl1-5 suggested that, in addition to the severe patterning defects, the mutants were maturing earlier than wild-type embryos. We performed global gene expression analysis of dcl1-15 and wild-type torpedo staged embryos to examine this maturation phenotype further. The results suggested that DCL1 is a heterochronic gene. Comparisons to a time series of embryo development (http://www.seedgenenetwork.net/arabidopsis) showed that the genes differentially expressed in dcl1-15 embryos behaved more like green-cotyledon stage embryos than torpedo embryos. Seeds of a DCL1/dcl1-15 plant were sown. For each wild-type sample, 300 torpedo stage embryos were selected from wild-type siblings. For each mutant replicate, 300 dcl1-15/dcl1-15 embryos were selected from the siliques of DCL1/dcl1-15 where the wild-type embryos were at the torpedo stage.
Project description:Transcription termination was analyzed by anti RNA pol II ChIP-seq in isogenic human HEK293 cell lines that inducibly express a-amanitin resistant mutants of the RNA polymerase II large subunit with slow and fast elongation rates and in lines that inducbily over-express WT or an active site mutant of the RNA exonuclease "torpedo" Xrn2.
Project description:We report a function of human mRNA decapping factors in control of transcription by RNA polymerase II. Decapping proteins Edc3, Dcp1a and Dcp2 and the termination factor TTF2 co-immunoprecipitate with Xrn2, the nuclear 5'-3' exonuclease torpedo that facilitates transcription termination at the 3' ends of genes. Dcp1a, Xrn2 and TTF2 localize near transcription start sites (TSSs) by ChIP-Seq. At genes with 5' peaks of paused pol II, knockdown of decapping or termination factors, Xrn2 and TTF2, shifted polymerase away from the TSS toward upstream and downstream distal positions. This re-distribution of pol II is similar in magnitude to that caused by depletion of the elongation factor Spt5. We propose that coupled decapping of nascent transcripts and premature termination by the torpedo mechanism is a widespread mechanism that limits bidirectional pol II elongation. Regulated co-transcriptional decapping near promoter-proximal pause sites followed by premature termination could control productive pol II elongation. RNA pol II (GSE30895: GSM766171), Xrn2, TTF2 and Dcp1a were localized by ChIP-Seq in HeLa cells. RNA pol II was localized in control HEK293 cells and cells infected with lentiviruses expressing a scrambled control shRNA (scr), and shRNAs targeting the following proteins: Xrn2, TTF2, Xrn2+TTF2, Edc3, Dcp1a, and Dcp2.