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Biosynthesis, membrane translocation, and surface expression of Sindbis virus E1 glycoprotein
G Migliaccio1, M C Pascale, A Leone
1Department of Biochemistry and Medical Biotechnology, University of Naples, Italy.
Experimental Cell Research
|November 1, 1989
Summary
Sindbis virus E1 glycoprotein can insert into the endoplasmic reticulum and reach the cell surface independently of the PE2 signal sequence, revealing internal signals for its transport.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Sindbis virus glycoproteins PE2 (precursor of E2) and E1 are essential for viral assembly and release.
- These glycoproteins are cotranslationally inserted into the endoplasmic reticulum membrane from a single mRNA.
- Previous studies identified a single N-terminal signal sequence in PE2 for translocation.
Purpose of the Study:
- To investigate the existence and function of internal signal sequences for Sindbis virus E1 glycoprotein.
- To determine if E1 can be independently translocated and transported in the absence of the PE2 signal sequence.
Main Methods:
- Generation of progressive deletions in the coding region upstream of E1.
- Engineering of modified cDNAs for in vitro transcription/translation and in vivo expression.
- Analysis of endoplasmic reticulum membrane insertion and cell surface transport of E1.
Main Results:
- Internal signal sequences upstream of E1 were identified, enabling independent ER membrane insertion.
- E1 protein is efficiently transported to the plasma membrane even without PE2/E2.
- E1 exit from the endoplasmic reticulum occurs at similar rates with or without PE2.
Conclusions:
- Sindbis virus E1 glycoprotein possesses internal signal sequences for independent membrane insertion and transport.
- E1's cellular localization and transport are not solely dependent on the PE2 signal sequence.
- These findings elucidate novel mechanisms for viral glycoprotein trafficking within the cell.