Ubiquitin-binding protein which acts as an adapter for ATPase cdc-48.1 and/or cdc-48.2, conferring substrate specificity (PubMed:20977550). Together with ubxn-2 and ubxn-3, plays a role in hermaphrodite spermatogenesis probably by promoting the degradation of sex determination terminal factor tra-1 (PubMed:20977550). Probably in association with ATPase cdc-48.1 or/and cdc-48.2, regulates the centrosomal levels of kinase air-1 levels during mitotic progression by promoting air-1 removal from centrosomes in prophase (PubMed:23649807). Also, regulates spindle orientation in the one-cell embryo by controlling centration and rotation of the pronuclei-centrosome complex in prophase (PubMed:23649807). Interacts with cdc-48.1 (via N-terminus) and cdc-48.2 (via N-terminus) (PubMed:20977550, PubMed:23649807). Interacts with kinase air-1 (PubMed:23649807). Colocalizes with cdc-48.1 to the perinuclear region in spermatocytes (PubMed:20977550). Nuclear localization is cdc-48-dependent (PubMed:23649807). During embryonic mitotic metaphase, telophase and to a certain extent prophase, localizes to centrosomes (PubMed:23649807). Expressed in the germline (at protein level) (PubMed:20977550). Expressed in spermatocytes but not in mature sperm (at protein level) (PubMed:20977550). Ubiquitously expressed (PubMed:17498661). Predominantly expressed in the spermatheca (PubMed:17498661). Expressed in embryos, larvae and adults. RNAi-mediated knockdown does not cause any visible phenotype (PubMed:20977550). Causes 82 percent embryonic lethality (PubMed:23649807). One-cell embryos have defects in pronuclei positioning and spindle orientation during prophase; however the duration of cell division and establishment of embryo polarity are normal (PubMed:23649807). During prophase, increases active air-1 and to a lesser extent zyg-9, plk-1 and spd-2, accumulation at centrosomes, centrosome size and microtubule growth rate (PubMed:23649807). Simultaneous RNAi-mediated knockdown of air-1 restores normal pronuclei positioning and spindle orientation but not embryonic lethality (PubMed:23649807). Simultaneous RNAi-mediated knockdown of ubxn-1 and ubxn-3, causes 50 percent embryonic lethality (PubMed:20977550). The surviving hermaphrodite progeny are sterile due to a lack of sperm (PubMed:20977550). Abnormal accumulation of sex determination terminal factor tra-1 (PubMed:20977550). Germline development is normal (PubMed:20977550). In males, sperm production is normal (PubMed:20977550). Belongs to the NSFL1C family.