The ZNF198 proline-rich region is crucial for protein–protein interaction.

(A) Truncated ZNF198–FGFR1 fusion proteins with (4ZFΔTK-HA and ΔZF-HA) or without (4ZFΔPRΔTK-HA) the ZNF198 proline-rich region were expressed individually (columns 2, 4, and 6), or were coexpressed with the full-length 4 zinc finger ZNF198–FGFR1 isoform (4ZF-MYC) (columns 3, 5, and 7). In vitro expressions were performed using reticulocyte lysates (Promega; in vitro TNT system) in the presence of [³⁵S] methionine. The proteins were analyzed directly (INP, input) or were immunoprecipitated with anti-HA or anti-MYC. Only fusion proteins containing the ZNF198 proline-rich region (columns 5 and 7) coprecipitated with full-length ZNF198–FGFR1. (B) A full-length 4 zinc finger ZNF198–FGFR1 isoform (4ZF-MYC) and a minipeptide containing only the ZNF198 proline-rich region (PR-HA) were expressed individually (columns 1 and 2) or coexpressed (column 3), then analyzed directly (INP) or immunoprecipitated with anti-HA or anti-MYC. PR-HA and 4ZF-MYC coprecipitated (column 3).