The polyribosomal protein bound to the 3' end of histone mRNA can function in histone pre-mRNA processing.

: Histone mRNAs end in a conserved 26 nt sequence which can form a stem-loop with a six-base stem and a four base loop. The 3' end of histone mRNA functions in the nucleus in pre-mRNA processing and mRNA transport and in the cytoplasm in translation and regulation of histone mRNA stability. The stem-loop binding protein (SLBP), found in both the polyribosomes and the nucleus, binds to the 3' end of histone mRNA. A nuclear extract which efficiently processes histone pre-mRNA has been prepared from mouse myeloma cells. The factors which bind the 3' end of histone mRNA can be depleted from this extract using a biotinylated oligonucleotide. Using the depleted extract, we show that the SLBP found in the polyribosomes can function in histone pre-mRNA processing, suggesting that the SLBP associates with histone pre-mRNA in the nucleus and accompanies the mature mRNA to the cytoplasm.