Protein implicated in polar growth%3B functionally redundant with Boi2p%3B interacts with bud-emergence protein Bem1p%3B contains an SH3 (src homology 3) domain and a PH (pleckstrin homology) domain%3B relocalizes from bud neck to cytoplasm upon DNA replication stress%3B BOI1 has a paralog%2C BOI2%2C that arose from the whole genome duplication