Exoribonuclease 1 (ERI1)

Metazoan replication-dependent histone mRNAs end in a highly conserved stem-loop structure that is required for regulation of histone mRNA stability and is bound by stem loop-binding protein (SLBP). Using the histone mRNA stem-loop sequence in RNA affinity purification assays, Dominski et al. (2003) isolated HEXO (histone mRNA end-specific exonuclease) protein from HeLa whole-cell extracts. They sequenced regions of HEXO protein using mass spectrometry and matched this protein to a full-length protein from a sequence database. HEXO encodes a 50-kD protein containing a SAP domain capable of recognizing AT-rich scaffold-attachment regions (SARs) in chromosomal DNA, and a exonuclease domain similar to those of DEDD exonuclease family members.