ESCRT-III-like protein involved in cytokinesis, nuclear envelope reassembly and endosomal tubulation (PubMed:19129479, PubMed:26040712, PubMed:28242692). Is required for efficient abscission during cytokinesis (PubMed:19129479). Involved in recruiting VPS4A and/or VPS4B to the midbody of dividing cells (PubMed:19129479, PubMed:19129480). During late anaphase, involved in nuclear envelope reassembly and mitotic spindle disassembly together with the ESCRT-III complex: IST1 acts by mediating the recruitment of SPAST to the nuclear membrane, leading to microtubule severing (PubMed:26040712). Recruited to the reforming nuclear envelope (NE) during anaphase by LEMD2 (PubMed:28242692). Regulates early endosomal tubulation together with the ESCRT-III complex by mediating the recruitment of SPAST (PubMed:23897888). {ECO:0000269|PubMed:19129479, ECO:0000269|PubMed:19129480, ECO:0000269|PubMed:23897888, ECO:0000269|PubMed:26040712, ECO:0000269|PubMed:28242692}. This is the function of Ensembl gene identifier ENSG00000182149 (IST1, IST1 factor associated with ESCRT-III).