The histone 3′ UTR stem-loop is an RNA element involved in nucleocytoplasmic transport of the histone mRNAs, and in the regulation of stability and of translation efficiency in the cytoplasm. The mRNAs of metazoan histone genes lack polyadenylation and a poly-A tail, instead 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.

• Williams AS, Marzluff WF (February 1995). "The sequence of the stem and flanking sequences at the 3′ end of histone mRNA are critical determinants for the binding of the stem-loop binding protein". Nucleic Acids Research. 23 (4): 654–662. doi:10.1093/nar/23.4.654. PMC 306734. PMID 7899087.
• Zanier K, Luyten I, Crombie C, Muller B, Schümperli D, Linge JP, Nilges M, Sattler M (January 2002). "Structure of the histone mRNA hairpin required for cell cycle regulation of histone gene expression". RNA. 8 (1): 29–46. doi:10.1017/s1355838202014061. PMC 1370228. PMID 11871659.
• Zhang M, Lam TT, Tonelli M, Marzluff WF, Thapar R (April 2012). "Interaction of the histone mRNA hairpin with stem-loop binding protein (SLBP) and regulation of the SLBP-RNA complex by phosphorylation and proline isomerization". Biochemistry. 51 (15): 3215–3231. doi:10.1021/bi2018255. PMC 3328597. PMID 22439849.