[The 161th lysine of C/EBPα in alveolar type II epithelial cells is modified by small ubiquitin-related modification]

Objective To clarify the interaction between CCAAT enhancer-binding protein α (C/EBPα) and small ubiquitin-related modification (SUMO) in human alveolar type II epithelial cells (AECII), and further identify its modification sites. Methods The expression of C/EBPα and SUMO1 in human AECII was detected by immunofluorescence double labeling. Co-IP was used to detect the interaction of C/EBPα and SUMO1 in AEC II. The SUMO site of C/EBPα was predicted to be the 161st lysine (K161) by the SUMOsp software. The wild-type GFP-C/EBPα plasmids and mutant GFP-K161R plasmids were constructed and transfected into AECII. The SUMO site of C/EBPα was identified by Co-IP. Results Immunofluorescence double staining found that SUMO1 and C/EBPα were co-located in the nucleus. C/EBPα-SUMO band could be marked by Co-IP, which suggested that C/EBPα could interact with SUMO1.When AECII was transfected by wild-type GFP-C/EBPα plasmids. C/EBPα-SUMO1 band could be detected by immunoprecipitation (IP), but could not be detected when transfected by mutant GFP-C/EBPα plasmids. These suggested that the SUMO site of C/EBPα was the 161st lysine. Conclusion C/EBPα can be modified by SUMO1 and the site of its modification is the 161st lysine in human AECII.