Fig. 1.

TheVari-X-linker cross-links proteins to RNA in seconds. a The Vari-X-linker standard lamps are ~10× more efficient in cross-linking proteins to RNA in vivo compared to the Megatron unit. Cells were UV irradiated in the Megatron for 100 s. Cross-linking in the Vari-X-linker was performed at the indicated times (seconds). The western blot shows that comparable amounts of Nab3 protein was purified during the CRAC experiments. The autoradiogram shows the ³²P-labeled RNA cross-linked to Nab3 in each sample. These scans were used to quantify the level of cross-linking relative to the Megatron by normalizing the autoradiogram signal to the protein levels. b As in a but now monitoring the cross-linking of the E. coli Hfq protein. c Results of PAR-CLIP experiments performed using variable 365 nm UV-irradiation times, indicated in seconds. For experimental details, see the Methods section