title: A carboxyl leucine-rich region of parathyroid hormone-related protein is critical for nuclear export.
abstract: PTHrP is an oncofetal protein with distinct proliferative and antiapoptotic roles that are affected by nucleocytoplasmic shuttling. The protein's nuclear export is sensitive to leptomycin B, consistent with a chromosome region maintenance protein 1-dependent pathway. We determined that the 109-139 region of PTHrP was involved in its nuclear export by demonstrating that a C-terminal truncation mutant, residues 1-108, exports at a reduced rate, compared with the wild-type 139 amino acid isoform. We searched for potential nuclear export sequences within the 109-139 region, which is leucine rich. Comparisons with established nuclear export sequences identified a putative consensus signal at residues 126-136. Deletion of this region resulted in nuclear export characteristics that closely matched those of the C-terminal truncation mutant. Confocal microscopic analyses of transfected 293, COS-1, and HeLa cells showed that steady-state nuclear levels of the truncated and deletion mutants were significantly greater than levels of wild-type PTHrP and were unaffected by leptomycin B, unlike the wild-type protein. In addition, both mutants demonstrated greatly reduced nuclear export with assays using nuclear preparations and intact cells. Based on these results, we conclude that the 126-136 amino acid sequence closely approximates the structure of a chromosome region maintenance protein 1-dependent leucine-rich nuclear export signal and is critical for nuclear export of PTHrP.
authors.affiliation: Division of Biological Sciences, University of California, San Diego, 92161, USA.
authors.forename: Jared C
authors.initials: JC
authors.lastname: Pache
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Burton
authors.forename: Leonard J
authors.initials: LJ
authors.lastname: Deftos
authors.forename: Randolph H
authors.initials: RH
authors.lastname: Hastings
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D006801:Humans; D007930:Leucine / Q000032:analysis; D008969:Molecular Sequence Data; D009154:Mutation; D049790:Nuclear Export Signals / Q000502:physiology*; D044162:Parathyroid Hormone-Related Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms; D017386:Sequence Homology, Amino Acid
chemical_list: D049790:Nuclear Export Signals; D044162:Parathyroid Hormone-Related Protein; D020033:Protein Isoforms; D007930:Leucine