Project description:For modified iCLIP experiment, 4SU was used for crosslinking as described in published protocol (citation is bellow) and the RNase conditions were optimised to ensure efficient RNase I-dependent fragmentation. In detail, HEK293T cells were grown on 10 cm 2 dishes, incubated for 8 h with 100 M 4SU and crosslinked with 2x 400mJ/cm 2 365nm UV light. Protein A Dynabeads were used for immunoprecipitations (IP). 80 l of beads were washed in iCLIP lysis buffer (50mM Tris-HCl pH 7.4, 100 mM NaCl, 1% NP-40, 0.1% SDS, 0.5% sodium deoxycholate). For the preparation of the cell lysate, 2 million cells were lysed in 1 ml of iCLIP lysis buffer (50 mM Tris-HCl pH 7.4, 100 mM NaCl, 1% NP-40, 0.1% SDS, 0.5% sodium deoxycholate) buffer, and the remaining cell pellet was dissolved in 50 L MSB lysis buffer (as above). After the pellet had dissolved, the mixture was diluted with CLIP lysis buffer to 1000 l and an additional centrifugation was performed. Lysates were pooled (2ml total volume) and incubated with 4 U/ml of RNase I and 2 l antiRNase (1/1000, AM2690, Thermo Fisher) at 37C for 3 min, and centrifuged. We took care to prepare the initial dilution of RNase in water, since we found that RNase I gradually loses its activity when diluted in the lysis buffer. 1.5 ml of the supernatant was then added to the beads and incubated at 4C for 4 h. The rest of the protocol was identical to the published protocol (see bellow). Huppertz I, Attig J, D'Ambrogio A, Easton LE, Sibley CR, Sugimoto Y, Tajnik M, Knig J, Ule J: iCLIP: protein-RNA interactions at nucleotide resolution. Methods 2014, 65:274-287.
Project description:ELAVL1 and CELF1 are two RNA-binding proteins involved in alternative splicing control. To address their functional relationships, we identify the differentially spliced mRNAs upon depletion of CELF1, ELAVL1, or both. These proteins control similar sets of genes with similar consequences on exon inclusion or skipping. The magnitude of the effect of the double depletion equals the sum of the magnitudes of the individual depletions, showing that CELF1 and ELAVL1 additively control their target RNAs. CELF1 and ELAVL1 regulated splicing events include ACSL4, WNK1, CD44, MICAL3, and JDP2. Using FRET, we find that CELF1 and ELAVL1 directly interact in cell nuclei. We demonstrate that the combined levels of CELF1 and ELAVL1 is a valuable biomarker in breast cancer, while their levels bring very limited information when taken individually. A “co-RNA splicing map” of CELF1 and ELAVL1 shows they repress alternative splice sites when bound nearby, but activate them when bound further away. Together, these data point to strong functional interactions between CELF1 and ELAVL1 to control alternative splicing with significant impacts in human pathology.
Project description:A stable HEK293 FlpIn T-Rex cells expressing TDP-43 with an N-terminal eGFP-tag was generated that allowed inducible physiological expression of the protein (Ling et al. 2010). Duplicate iCLIP experiments were performed using an antibody targeting eGFP (Abcam ab290). Crosslinked RNA-protein complexes were isolated by immuno-precipitation and cDNAs were generated to allow preparation of Illumina compatible DNA libraries as described in Huppertz et al. (2014).