Cleavage of pm7G from mRNA 5' terminal cap structures by pyrophosphatase activity in embryonic chick lens cells

The presence of pyrophosphatase activity in embryonic lens cells which cleaves pm7G and ppGm from m7G(5')pppGm was demonstrated. It was also found that m7G(5')pppG, but not G(5')pppG, was hydrolyzed, and conversion of m7GpppG to m7G*pppG, in which the 5-membered ring of the m7G moiety is open, abolished its hydrolysis. For the caps hydrolyzed, pm7G was released only in the presence of lens cellular fraction; pm7G inhibited cap hydrolysis.