Present address: Université Laval, Centre de Recherches en Infectiologie, Sainte Foy, Québec GIV 4G2, Canada.
Degradation signals within both terminal domains of the cauliflower mosaic virus capsid protein precursor
Article first published online: 23 DEC 2001
The Plant Journal
Volume 27, Issue 4, pages 335–343, 2001
How to Cite
Karsies, A., Hohn, T. and Leclerc, D. (2001), Degradation signals within both terminal domains of the cauliflower mosaic virus capsid protein precursor. The Plant Journal, 27: 335–343. doi: 10.1046/j.1365-313x.2001.01093.x
- Issue published online: 23 DEC 2001
- Article first published online: 23 DEC 2001
- Received 19 March 2001; revised 8 May 2001; accepted 24 May 2001.
- degradation signals;
- cauliflower mosaic virus;
- capsid protein;
- ubiquitin protein reference technique;
- PEST motif
Targeted protein degradation plays an important regulatory role in the cell, but only a few protein degradation signals have been characterized in plants. Here we describe three instability determinants in the termini of the cauliflower mosaic virus (CaMV) capsid protein precursor, of which one is still present in the mature capsid protein p44. A modified ubiquitin protein reference technique was used to show that these motifs are still active when fused to a heterologous reporter gene. The N-terminus of p44 contains a degradation motif characterized by proline, glutamate, aspartate, serine and threonine residues (PEST), which can be inactivated by mutation of three glutamic acid residues to alanines. The signals from the precursor do not correspond to known degradation motifs, although they confer high instability on proteins expressed in plant protoplasts. All three instability determinants were also active in mammalian cells. The PEST signal had a significantly higher degradation activity in HeLa cells, whereas the precursor signals were less active. Inhibition studies suggest that only the signal within the N-terminus of the precursor is targeting the proteasome in plants. This implies that the other two signals may target a novel degradation pathway.