Project description:To determine the transcription start site and the abundance of dam mRNA, we conducted mRNA-specific RNA-Seq experiments. Essentially two strategies were tested. First strategy: We obtained the cDNA with a specific RT-PCR in order to get the mRNA from our dam construct (see DNA-seq of DamID reporter cassette). An enrichment, in which we used a Biotinylated dam oligo and Streptavidin magnetic beads, was needed. Then, similar to SHAPE-seq, the ssDNA ligation was performed with CircLigase. The last step was the PCR reaction in order to prepare the cDNA libraries to be sequenced. Second strategy: Similar to the first one, but the specificity was introduced at the PCR, not at the RT. Thereby, busk cDNA was prepared with random hexamers. The enrichment step was not needed.
Project description:Quantitative analysis of the sequence determinants of transcription and translation regulation is of special relevance for systems and synthetic biology applications. Here, we developed a novel generic approach for the fast and efficient analysis of these determinants in vivo. ELM-seq (expression level monitoring by DNA methylation) uses Dam coupled to high-throughput sequencing) as a reporter that can be detected by DNA-seq. We used the genome-reduced bacterium Mycoplasma pneumoniae to show that it is a quantitative reporter. We showed that the methylase activity correlates with protein expression, does not affect cell viability, and has a large dynamic range (~10,000-fold). We applied ELM-seq to randomized libraries of promoters or 5’ untranslated regions. We found that transcription is greatly influenced by the bases around the +1 of the transcript and the Pribnow box, and we also identified several epistatic interactions (including the +1 and the “extended Pribnow”). Regarding translation initiation, we confirmed that the Shine-Dalgarno motif is not relevant, but instead, that RNA secondary structure is the main governing factor. With this in hand, we developed a predictor to help tailor gene expression in M. pneumoniae. The simple ELM-seq methodology will allow identifying and optimizing key sequence determinants for promoter strength and translation. The ELM-seq methodology allows both researchers and companies to identify and optimize in an easy and comprehensive manner, key sequence determinants for promoter strength and translation.
Project description:Dam identification (DamID) is a powerful technique to generate genome-wide maps of chromatin protein binding. Due to its high sensitivity it is particularly suited to study the genome interactions of chromatin proteins in small tissue samples in model organisms such as Drosophila. Here we report an intein-based approach to tune the expression level of Dam and Dam-fusion proteins in Drosophila by addition of a ligand to fly food. This helps to suppress toxic effects of Dam. In addition we describe a strategy for genetically controlled expression of Dam in a specific cell type in complex tissues. We demonstrate the utility of the latter by generating a glia-specific map of Polycomb in small samples of brain tissue. RNA sequencing of 3 samples, each using 2 biological replicates.