Purified early spermatids (approximately 5×106 cells) from HA-tagged Ddx19b KI and WT control mice were lysed in IP lysis buffer (50 mM Tris-HCl pH 7.4, 150 mM NaCl, 1 mM EDTA, 1% NP-40, and protease inhibitors). Lysates were clarified by centrifugation and incubated with anti-HA magnetic beads overnight at 4°C. Beads were washed extensively, and bound proteins were eluted with 0.1 M glycine-HCl pH 2.5. Eluted proteins were neutralized, reduced, alkylated, and digested with trypsin. The resulting peptides were analyzed by nano-LC-MS/MS on an Orbitrap Fusion Lumos mass spectrometer. Peptide identification and label-free quantification were performed using MaxQuant software against the UniProt mouse database. The protein intensitiesof all identified proteins were normalized bytotal intensity and then used for differentialprotein expression analysis using DEqMS(Zhu et al. 2020). Proteins with a log2FC > 2 and an FDR < 0.01 were considered significant interactors.