By library screening we identified two proteins (HOMER3 and DNCL1) that interact with the C-terminal peptide and three proteins (HOMER3, DNCL1 and TRIM11) that interact with the whole PST domain. This suggests that HOMER3 and DNCL1 interact specifically with the C-terminal peptide while TRIM11 interacts with a more N-terminal part of the PST domain. We conducted pairwise tests between specific constructs to confirm the interactions identified in the library screen and to further investigate the interaction between PAX6 and HOMER3, DNCL1 and TRIM11. The Dncl1 and Trim11 clones that were pulled out of the library were full-length, but the Homer3 cDNAs lacked the N-terminal 70 amino acids. The missing coding region was inserted into the truncated Homer3 cDNA to give a full-length expression construct (see Methods). Pairwise interactions were carried out with both the full-length and truncated Homer3 clones.