(A–B) BTH-capped luciferase mRNA ending in a histone stemloop (LUC-SL, panel A) or tetraloop (LUC-TL, panel B) was nucleoporated into synchronized HeLa cells that were then treated with HU, and RNA was isolated 30 min after HU treatment. These are the same RNA samples that were previously analyzed (Su et al., 2013). Results with a set of ARCA capped mRNAs is shown in Supp. Fig. 4.
(C) Possible pathways of histone mRNA degradation initiated at the 3′ end of histone mRNA.