Project description:Membrane-bound transcription factor CREB3L1 undergoes Regulated Intramembrane Proteolysis (RIP) in response to Hepatitis C infection. RIP activates CREB3L1 so that it can prevent the growth of HCV infected cells through the action of downstream genes. We over-expressed a truncated form of CREB3L1 that does not require RIP to enter the nucleus. Cells over-expressing this truncated form were isolated by Fluorescence Activated Cell Sorting (FACS). We used microarray to determine the downstream genes of CREB3L1 in comparison to a flow sorted empty vector control. HCV Replicon-containing cells were transfected with a CREB3L1Δ381-519 to determine the downstream genes.
Project description:Membrane-associated, integral membrane and secreted proteins are of key importance in many cellular processes. For most of the 28 952 predicted proteins in Arabidopsis, the actual subcellular localisation has not been demonstrated experimentally. So far, their potential membrane-association has been deduced from algorithms that predict transmembrane domains and signal peptides. However, the comprehensiveness and accuracy of these algorithms is still limited. The majority of membrane-associated and secreted proteins is synthesised on membrane-bound polysomes. Therefore, the isolation and characterisation of mRNA associated with membrane-bound polysomes offers an experimental tool for the genome-wide identification of these proteins. Here we describe an efficient method to isolate mRNA from membrane-bound polysomes and report on the validation of the method to enrich for transcripts encoding membrane-associated and secreted proteins. The sensitivity and reproducibility of the isolation method was investigated by DNA microarray analysis. Pearson correlations between transcript levels obtained from three replicate isolations showed that the method is highly reproducible. A significant enrichment for mRNAs encoding proteins containing predicted transmembrane domains and signal peptides was observed in the membrane-bound polysomal fraction. In this fraction, 301 transcripts were classified by gene ontologies as âcellular component unknownâ, and potentially encode previously unrecognised secreted or membrane-associated proteins. Membrane-bound (MBP) and free polysomes (FP) were isolated in triplicate from one batch of two weeks old aboveground parts of Arabidopsis seedlings. Each combination of isolated MBP and FP was applied to 4 microarrays, of which two were dyeswapped, giving a total of 12 arrays.
Project description:Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. mRNA species bound to membrane-associated polysomes were separated from other mRNAs by sedimentation equilibrium or sedimentation velocity. The distribution of individual transcripts in the 'membrane-bound' and 'cytosolic' fractions was quantitated for thousands of genes by hybridization to DNA microarrays. Transcripts known to encode secreted or membrane proteins were enriched in the membrane-bound fractions, whereas those known to encode cytoplasmic proteins were enriched in the fractions containing mRNAs associated with free and cytoplasmic ribosomes. On this basis, we identified over 275 human genes and 285 yeast genes that are likely to encode previously unrecognized secreted or membrane proteins. Computed