▁ ▁which ▁is ▁responsible ▁for ▁the ▁reg ulation ▁of ▁the ▁length ▁of ▁the ▁poly A ▁tail ▁of ▁the ▁U 1 A ▁protein ▁pre - m R NA . ▁The ▁P IE ▁is ▁located ▁in ▁the ▁U 1 A ▁m R NA ▁ 3 ' ▁U TR . ▁P IE ▁adopt s ▁a ▁U - sh aped ▁structure , ▁with ▁binding ▁sites ▁for ▁a ▁single ▁U 1 A ▁protein ▁at ▁each ▁b end ▁and ▁when ▁complex ed ▁with ▁the ▁two ▁prote ins ▁it ▁blocks ▁activity ▁of ▁poly ( A ) ▁polym er ase ▁( P AP ), ▁and ▁in hib its ▁its ▁activity . ▁ ▁References ▁ ▁External ▁links ▁▁▁▁ ▁Category : C is - reg ul atory ▁R NA ▁elements <0x0A> </s> ▁John ▁J . ▁Spe ar man ▁( Dec ember ▁ 1 7 , ▁ 1 8 2 4 ▁- ▁May ▁ 3 1 , ▁ 1 9 1 1 ) ▁was ▁a ▁ 1 9 th - century ▁American ▁iron ▁manufact urer , ▁for em ost ▁among ▁the ▁iron ▁manufact ur ers ▁of ▁his ▁era , ▁and ▁for ▁many ▁years ▁identified ▁with ▁the ▁bank ing ▁interests ▁of ▁Sh aron , ▁Pennsylvania . ▁ ▁Early ▁life ▁He ▁was ▁born ▁in ▁Mc ▁K ee ’ s ▁G ap , ▁Bla ir ▁County , ▁Pennsylvania . ▁His ▁parents ▁were ▁Francis ▁and ▁Elizabeth ▁( Am bro se ) ▁Spe ar man . ▁His ▁father ▁was ▁born ▁in ▁Kent ▁county , ▁Maryland , ▁of ▁English ▁origin . ▁His ▁mother ▁was ▁born ▁near ▁Mc Con n ells