Regulatory subunit (beta subunit) of the cytosolic type I platelet-activating factor (PAF) acetylhydrolase (PAF-AH (I)), an enzyme that catalyzes the hydrolyze of the acetyl group at the sn-2 position of PAF and its analogs and participates in the PAF inactivation (PubMed:10542206). Regulates the PAF-AH (I) activity in a catalytic dimer composition-dependent manner (PubMed:10542206). Positively regulates the activity of the minus-end directed microtubule motor protein dynein. May enhance dynein-mediated microtubule sliding by targeting dynein to the microtubule plus end. Required for several dynein- and microtubule-dependent processes such as the maintenance of Golgi integrity, the peripheral transport of microtubule fragments and the coupling of the nucleus and centrosome. Required during brain development for the proliferation of neuronal precursors and the migration of newly formed neurons from the ventricular/subventricular zone toward the cortical plate. Neuronal migration involves a process called nucleokinesis, whereby migrating cells extend an anterior process into which the nucleus subsequently translocates. During nucleokinesis dynein at the nuclear surface may translocate the nucleus towards the centrosome by exerting force on centrosomal microtubules. Also required for proper activation of Rho GTPases and actin polymerization at the leading edge of locomoting cerebellar neurons and postmigratory hippocampal neurons in response to calcium influx triggered via NMDA receptors. May also play a role in other forms of cell locomotion including the migration of fibroblasts during wound healing (By similarity). Required for pronuclear migration during fertilization. Required for dynein recruitment to microtubule plus ends and BICD2-bound cargos (By similarity). May modulate the Reelin pathway through interaction of the PAF-AH (I) catalytic dimer with VLDLR (By similarity). Can self-associate. Component of the cytosolic PAF-AH (I) heterotetrameric enzyme, which is composed of PAFAH1B1 (beta), PAFAH1B2 (alpha2) and PAFAH1B3 (alpha1) subunits. The catalytic activity of the enzyme resides in the alpha1 (PAFAH1B3) and alpha2 (PAFAH1B2) subunits, whereas the beta subunit (PAFAH1B1) has regulatory activity. Trimer formation is not essential for the catalytic activity (PubMed:10542206). Interacts with the catalytic dimer of PAF-AH (I) heterotetrameric enzyme: interacts with PAFAH1B2 homodimer (alpha2/alpha2 homodimer), PAFAH1B3 homodimer (alpha1/alpha1 homodimer) and PAFAH1B2-PAFAH1B3 heterodimer (alpha2/alpha1 heterodimer) (PubMed:10940388). Interacts with DCX, IQGAP1, KATNB1, NDEL1, NUDC and RSN. Interacts with DISC1, and this interaction is enhanced by NDEL1. Interacts with DAB1 when DAB1 is phosphorylated in response to RELN/reelin signaling (By similarity). Interacts with dynein and NDE1 (PubMed:10940388, PubMed:11056532). Interacts with dynactin (PubMed:11056532, PubMed:14584027). Localizes to the plus end of microtubules and to the centrosome. Redistributes to axons during neuronal development. Also localizes to the microtubules of the manchette in elongating spermatids and to the meiotic spindle in spermatocytes (By similarity). May localize to the nuclear membrane. Expression increases during fertilization of the oocyte. Dimerization mediated by the LisH domain may be required to activate dynein. Originally the subunits of the type I platelet-activating factor (PAF) acetylhydrolase was named alpha (PAFAH1B1), beta (PAFAH1B2) and gamma (PAFAH1B3) (By similarity). Now these subunits have been renamed beta (PAFAH1B1), alpha2 (PAFAH1B2) and alpha1 (PAFAH1B3) respectively (By similarity). Belongs to the WD repeat LIS1/nudF family.