As ▁in ▁turn ▁suggests ▁that ▁Down stream - pe pt ide ▁R N As ▁are ▁also ▁rib os w itch es . ▁Second , ▁Down stream - pe pt ides ▁are ▁consist ently ▁position ed ▁in ▁a ▁place ▁that ▁is ▁consistent ▁with ▁a ▁c is - reg ul atory ▁role ▁in ▁reg ulating ▁the ▁down stream ▁OR F s , ▁although ▁the ▁bi ological ▁role ▁of ▁the ▁OR F s ▁is ▁unknown . ▁Third , ▁the ▁pseud ok not ▁structure ▁has ▁a ▁moder ate ▁complexity ▁that ▁is ▁typical ▁of ▁rib os w itch es . ▁ ▁Finally , ▁the ▁observation ▁of ▁reg ulation ▁of ▁a ▁down stream ▁OR F ▁by ▁nit ro gen ▁avail ability ▁also ▁suggests ▁a ▁c is - reg ul atory ▁role ▁of ▁the ▁element . ▁ ▁This ▁hypothesis ▁is ▁supported ▁by ▁bio chem ical ▁and ▁gen etic ▁data . ▁ ▁First , ▁both ▁Down stream - pe pt ide ▁R N As ▁and ▁g ln A ▁R N As ▁select ively ▁bind ▁gl ut am ine . ▁ ▁Second , ▁rep orter ▁gene ▁analysis ▁of ▁the ▁Down stream - pe pt ide ▁mot if ▁revealed ▁that ▁this ▁R NA ▁prom otes ▁rep orter ▁gene ▁expression ▁upon ▁binding ▁of ▁gl ut am ine ▁and ▁can ▁therefore ▁be ▁considered ▁an ▁activ ating ▁rib os w itch . ▁Possible ▁candidates ▁to ▁be ▁reg ulated ▁by ▁the ▁Down stream - pe pt ide ▁mot if ▁are ▁gen es ▁that ▁frequently ▁carry ▁the ▁Down stream - pe pt ide ▁mot if ▁in ▁their ▁