▁e uk ary otic ▁rib os om es , ▁four ▁m ature ▁rib os om al ▁R N As ▁( the ▁ 5 S , ▁ 5 . 8 S , ▁ 1 8 S , ▁and ▁ 2 5 S ) ▁must ▁be ▁synth es ized . ▁ ▁Three ▁of ▁these ▁r R N As ▁( 5 . 8 S , ▁ 1 8 S , ▁and ▁ 2 5 S ) ▁come ▁from ▁a ▁single ▁pre - r R NA ▁known ▁as ▁the ▁ 3 5 S . ▁ ▁Although ▁many ▁of ▁the ▁inter medi ates ▁in ▁this ▁r R NA ▁processing ▁path way ▁have ▁been ▁identified ▁in ▁the ▁last ▁thirty ▁years , ▁there ▁are ▁still ▁a ▁number ▁of ▁prote ins ▁involved ▁in ▁this ▁process ▁whose ▁specific ▁function ▁is ▁unknown . ▁ ▁Function ▁▁ ▁Sh q 1 , ▁a ▁protein ▁thought ▁to ▁play ▁a ▁role ▁in ▁the ▁stabil ization ▁and / or ▁production ▁of ▁box ▁H / AC A ▁s no R NA , ▁is ▁still ▁un character ized . ▁ ▁It ▁has ▁been ▁proposed ▁that ▁Sh q 1 , ▁along ▁with ▁N af 1 p , ▁is ▁involved ▁in ▁the ▁initial ▁steps ▁of ▁the ▁bi ogen esis ▁of ▁H / AC A ▁box ▁s no R NP s ▁( box ▁H / AC A ▁s no R N As ▁form ▁complex es ▁with ▁prote ins , ▁thereby ▁forming ▁s no R NP s ) ▁because ▁of ▁its ▁association ▁with ▁certain ▁s no R NP ▁prote ins ▁during ▁the ▁s no