R NA ▁editing ▁was ▁the ▁first ▁example ▁of ▁editing ▁observed ▁in ▁verte br ates . ▁Edit ing ▁of ▁A po B ▁m R NA ▁occurs ▁in ▁all ▁pla cent al ▁m amm als . ▁Edit ing ▁occurs ▁post ▁trans cription ally ▁as ▁the ▁nas cent ▁pol yn uc le ot ides ▁do ▁not ▁contain ▁edited ▁nucle os ides . ▁ ▁Type ▁C ▁to ▁U ▁editing ▁of ▁A po B ▁m R NA ▁requires ▁an ▁editing ▁complex ▁or ▁h olo enz yme ▁( edit os ome ) ▁consisting ▁of ▁the ▁C ▁to ▁U - edit ing ▁en zym e ▁Apol ip op rote in ▁B ▁m R NA ▁editing ▁en zym e , ▁catal yt ic ▁pol ype pt ide ▁ 1 ▁( A po B EC - 1 ) ▁as ▁well ▁as ▁other ▁auxili ary ▁factors . ▁A po B EC - 1 ▁is ▁a ▁protein ▁that ▁in ▁humans ▁is ▁encoded ▁by ▁the ▁AP OB EC 1 ▁gene .[ 1 ] It ▁is ▁a ▁member ▁of ▁the ▁c yt id ine ▁de amin ase ▁family . ▁A po B EC - 1 ▁alone ▁is ▁not ▁sufficient ▁for ▁the ▁editing ▁of ▁A po B ▁m R NA ▁ ▁and ▁requires ▁at ▁least ▁ ▁one ▁of ▁these ▁ ▁auxili ary ▁factors , ▁AP OB EC 1 ▁complement ation ▁factor ▁( A 1 CF ) ▁for ▁editing ▁to ▁occur . ▁A 1 CF ▁contains ▁ 3 ▁non ▁identical ▁repe ats . ▁It ▁acts ▁as ▁the ▁R NA ▁binding ▁sub unit ▁and ▁direct s ▁A po B