Back to Search
Start Over
The Signal Peptide of the Mouse Mammary Tumor Virus Rem Protein Is Released from the Endoplasmic Reticulum Membrane and Accumulates in Nucleoli
- Source :
- Journal of Biological Chemistry. 283:9966-9976
- Publication Year :
- 2008
- Publisher :
- Elsevier BV, 2008.
-
Abstract
- N-terminal signal sequences mediate endoplasmic reticulum (ER) targeting and insertion of nascent secretory and membrane proteins and are, in most cases, cleaved off by signal peptidase. The mouse mammary tumor virus envelope protein and its alternative splice variant Rem have an unusually long signal sequence, which contains a nuclear localization signal. Although the envelope protein is targeted to the ER, inserted, and glycosylated, Rem has been described as a nuclear protein. Rem as well as a truncated version identical to the cleaved signal sequence have been shown to function as nuclear export factors for intron-containing transcripts. Using transiently transfected cells, we found that Rem is targeted to the ER, where the C-terminal portion is translocated and glycosylated. The signal sequence is cleaved off and accumulates in nucleoli. In a cell-free in vitro system, the generation of the Rem signal peptide depends on the presence of microsomal membranes. In vitro and in cells, the signal peptide initially accumulates in the membrane and is subsequently released into the cytosol. This release does not depend on processing by signal peptide peptidase, an intramembrane cleaving protease that can mediate the liberation of signal peptide fragments from the ER membrane. Our study suggests a novel pathway by which a signal peptide can be released from the ER membrane to fulfill a post-targeting function in a different compartment.
- Subjects :
- Signal peptide
Cytoplasm
Glycosylation
Nuclear Localization Signals
Active Transport, Cell Nucleus
Target peptide
Biology
Endoplasmic Reticulum
Biochemistry
Mice
Viral Envelope Proteins
Mammary tumor virus
Microsomes
Chlorocebus aethiops
Animals
Humans
Nuclear export signal
Molecular Biology
Signal peptidase
Endoplasmic reticulum
Intracellular Membranes
Cell Biology
Molecular biology
Protein Structure, Tertiary
Cell biology
Mammary Tumor Virus, Mouse
Membrane protein
COS Cells
Signal peptide peptidase
HeLa Cells
Protein Modification, Translational
Subjects
Details
- ISSN :
- 00219258
- Volume :
- 283
- Database :
- OpenAIRE
- Journal :
- Journal of Biological Chemistry
- Accession number :
- edsair.doi.dedup.....01044f411dda15abaa228c8b2e782893