Add reference In an attempt to identify proteins interacting with transcription factor E2F2, proteins extracted from HA-E2F2 overexpressing HEK293T cells were were subjected to immunoprecipitation (IP) with an anti-HA antibody or, as a negative control (NegCt), with an anti-T antibody. Immunoprecipitated proteins were eluted, digested with trypsin, and the resulting peptides were analyzed by LC-MS/MS. The whole procedure was repeated several times in an attempt to gauge reproducibility (nine replicates of the anti-HA IP and six replicates of the control IP).