To identify an RNP interactome of Unr, V5 tagged wildtype protein and a mutant containing several interdomain contacts, that shows reduced protein expression were tansfected in SL2 cells after a siRNA knoch-down of the endogenous protein levels. After pulling down the transfected protein with an antibody against the V5-tag differences interacting proteins were identified using mass spectrometry. One set was done with an RNase treatment and one without, to identify interaction partners that rely on RNA binding. The lower expression level of the mutant protein allowed us to take this as a specific background control.