Self-inactivating lentiviruses expressing green fluorescent protein (GFP), hemagglutinin (HA)-tagged NFI dominant repressor (NFI/EnR), or Drosophila engrailed repressor domain alone (EnR), constitutively active FLAG-tagged NFATc4 (NFATc4-Ala), or constitutively active calcineurin (CaN) were described previously (Wang et al., 2004 (link); Ding et al., 2013 (link), 2016 (link)). These plasmids are available upon request. MEK5-DN lentivirus was also described previously (Doebele et al., 2009 (link)). Human embryonic kidney 293T cells (American Type Culture Collection) were grown in DMEM (Invitrogen) containing 10% heat-inactivated fetal bovine serum (Invitrogen).