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Updated: Aug 8, 2026

Visualization of Endoplasmic Reticulum Localized mRNAs in Mammalian Cells
Published on: December 17, 2012
Cell density-dependent nuclear/cytoplasmic localization of NORPEG (RAI14) protein
R Krishnan Kutty1, Shanyi Chen, William Samuel
1Section on Biochemistry, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA. kuttyk@nei.nih.gov
Abstract:
NORPEG (RAI14), a developmentally regulated gene induced by retinoic acid, encodes a 980 amino acid (aa) residue protein containing six ankyrin repeats and a long coiled-coil domain [Kutty et al., J. Biol. Chem. 276 (2001), pp. 2831-2840]. We have expressed aa residues 1-287 of NORPEG and used the recombinant protein to produce an anti-NORPEG polyclonal antibody. Confocal immunofluorescence analysis showed that the subcellular localization of NORPEG in retinal pigment epithelial (ARPE-19) cells varies with cell density, with predominantly nuclear localization in nonconfluent cells, but a cytoplasmic localization, reminiscent of cytoskeleton, in confluent cultures. Interestingly, an evolutionarily conserved putative monopartite nuclear localization signal (P(270)KKRKAP(276)) was identified by analyzing the sequences of NORPEG and its orthologs. GFP-NORPEG (2-287 aa), a fusion protein containing this signal, was indeed localized to nuclei when expressed in ARPE-19 or COS-7 cells. Deletion and mutation analysis indicated that the identified nuclear localization sequence is indispensable for nuclear targeting.
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