Detection of IGF2BP1 phosphorylation in vitro and in vivo via Pro-Alanase treatment

In this project we aim to identify phosphorylation sites of IGF2BP1 that have not been discovered yet in mass spec experiments due to insufficient coverage. To this end we used Pro-Alanase treatment that produced detectable peptides in regions that are not covered by commonly used approaches. IGF2BP1 phosphorylation was investigated in vitro by treating purified IGF2BP1 with Src and in vivo by comparing immunoprecipitated IGF2BP1 from unstressed and stressed (1.5 h thapsigargin or 2 h or arsenite) HEK293T cells expressing GFP-labeled IGF2BP1.