Figure 1.

Cytoplasmic histone mRNAs. (a) A schematic of a mammalian histone mRNA showing the cap on the 5′ end, the short 5′ and 3′ UTRs and the stemloop at the 3′ end, which is bound by SLBP and 3′hExo. (b) Histone mRNA regulation during the cell cycle. Histone mRNAs increase just before entry into S-phase and decrease at the end of S-phase [2]. The levels of SLBP protein are also cell cycle regulated [1], while there is very little change in SLBP mRNA levels. Inhibition of DNA replication during S-phase (dotted line) results in rapid degradation of histone mRNA but not of SLBP. (c) The 3′ ends of the HIST2H2AA3 mRNAs from HCT116 S-phase cells, determined by high-throughput sequencing using the End-Seq approach [7]. The x-axis displays the nts at the 3′ end of the mRNA, with numbers referring to the drawing of the stemloop. The bars indicate the number of RNAs (y-axis) that have their last templated nt at that position. Blue indicates the RNA ends with the last templated nt, green indicates there was a single U added at that site, orange indicates there were two Us added at that site, and red indicates that there were more than 2 nts added at that site.