Histone 3' UTR stem-loop

The Histone 3' UTR stem-loop is an RNA element involved in nucleocytoplasmic transport of the mRNA, and in stability regulation and translation efficiency in the cytoplasm. The mRNAs of metazoan histone genes lack a poly-A tail. 3' end processing occurs at a site between this highly conserved stem-loop and a purine rich region around 20 nucleotides downstream (the histone downstream element, or HDE). The stem-loop is bound by a 31 kDa stem-loop binding protein (SLBP - also termed the histone hairpin binding protein, or HBP). Together with U7 snRNA binding of the HDE, SLBP binding nucleates the formation of the processing complex.