Involved in the maintenance of the Golgi structure. Interacts with YIPF3 and YIPF5. (Microbial infection) Interacts with human papillomavirus (HPV) E5 proteins. Expressed in keratinocytes (at protein level). In primary foreskin keratinocytes, down-regulated during calcium-induced differentiation (at protein level). The physiological relevance of this observation is unclear as YIPF4 protein is expressed throughout the epithelial layers in organotypic raft cultures, a cell-culture model of stratified epithelium. (Microbial infection) Down-regulation upon calcium-induced keratinocyte differentiation is prevented in the presence of human papillomavirus (HPV), independently of HPV E5 protein (at protein level). The physiological relevance of this observation is unclear. Belongs to the YIP1 family.