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Updated: Aug 15, 2026

Visualization of Endoplasmic Reticulum Localized mRNAs in Mammalian Cells
Published on: December 17, 2012
ERj1p has a basic role in protein biogenesis at the endoplasmic reticulum
Johanna Dudek1, Markus Greiner, Anika Müller
1Medizinische Biochemie und Molekularbiologie, Universität des Saarlandes, D-66421 Homburg, Germany.
Abstract:
ERj1p is a membrane protein of the endoplasmic reticulum (ER) that can recruit the ER lumenal chaperone BiP to translating ribosomes. ERj1p can also modulate protein synthesis at initiation and is predicted to be a membrane-tethered transcription factor. Here we attribute the various functions of ERj1p to distinct regions within its cytosolic domain. A highly positively charged nonapeptide within this domain is necessary and sufficient for binding to ribosomes. Binding of ERj1p to ribosomes involves the 28S ribosomal RNA and occurs at the tunnel exit. Additionally, ERj1p has a dual regulatory role in gene expression: ERj1p inhibits translation in the absence of BiP, and another charged oligopeptide within the cytosolic domain of ERj1p mediates binding of the nuclear import factor importin beta and import into the nucleus, thereby paving the way for subsequent action on genomic DNA.
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