Unrip is part of the SMN complex that plays a role in snRNP assembly in the cytoplasm and pre mRNA splicing in the nucleus. Unrip interacts directly with Gemin 6 and Gemin 7 in the SMN complex. It is associated with the complex in the cytoplasm but not in the nucleus and thus is thought to play a role in it's subcellular localisation. It is a ubiquitously expressed protein that acts as an inhibitor of TGF-beta signaling and an important regulator of cell proliferation. Stable expression of STRAP results in activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway and in down-regulation of the cyclin-dependent kinase inhibitor p21 (Cip1), which results in retinoblastoma protein hyperphosphorylation. Upregulation of STRAP might play a role in tumor development as an early event for colorectal cancers. It is the first component of the U snRNP assembly machinery that associates with SMN complex in a compartment-specific way and plays a crucial role in the intracellular distribution of SMN1.