10         20         30         40         50         60
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MLCEDQHMSV ENTPQKGSGS LNSSASSISI DVKPTMQSWA QEVRAEFGHS DEASSSLNSS - 60
AASCGSLAKK ETADGNLESK DGEGREMAFE FLDGVNEVKF ERLVKEEKLK TPYKRRHSFT - 120
PPSNENSRSN SPNSSNSSAN GDAAAPKGGN NPHSRNSKKS GNFRAHKEEK RVRHNSYTSS - 180
TSSSSSYTEA DPAILSRRQK QIDYGKNTAA YERYVEMVPK DERTRDHPRT PNKYGKYSRR - 240
AFDGLVKIWR KSLHIYDPPT QARDTAKDSN SDSDSD

Stem-loop binding protein (SLBP) is a 31 kDa protein that is central to the regulation of histone mRNAs and is highly conserved in metazoans. It is involved in histone pre-mRNA 3' processing and couples histone mRNA production with the cell cycle. Both maternal and zygotic proteins play an essential and vital function for development. The SLBP, which binds the conserved 26 nucleotide hairpin at the 3' end of all metazoan replication-dependent histone mRNAs, is important for regulation of histone mRNA processing, translation, and degradation. In vertebrate and Drosophila SLBPs, the region required for RNA binding and pre-mRNA processing is located toward the C-terminal end. dSLBP has a two-domain structure with the RNA binding and processing domain (residues 175-276) in the C-terminal half of the molecule. Drosophila genetics suggests that dSLBP also shuttles between the nucleus and the cytoplasm implicating a cytoplasmic role for the N-terminal domain of dSLBP, but no function has yet been assigned to residues 1-173.