Chez Charles/ biblio/ Reversal of T4 RNA ligase. Edit RecentChanges History Preferences Branchable Krug M, Uhlenbeck OC. Biochemistry. 1982 Apr 13;21(8):1858-64. Reversal of T4 RNA ligase. T4RNL1 & AMP can remove or exchange 3′ phosphate from RNA molecles. Thus, 3′-P is not a good blocking group.