Degradation signals within both terminal domains of the cauliflower mosaicvirus capsid protein precursor

Karsies, A Hohn, T Leclerc, D

A. Karsies et al., Degradation signals within both terminal domains of the cauliflower mosaicvirus capsid protein precursor, PLANT J, 27(4), 2001, pp. 335-343

36

INGLESE

Article

Plant Sciences","Animal & Plant Sciences

PLANT JOURNAL

0960-7412 → ACNP

27

4

2001

335 - 343

ISI

0960-7412(200108)27:4<335:DSWBTD>2.0.ZU;2-5

Targeted protein degradation plays an important regulatory role in the cell , but only a few protein degradation signals have been characterized in pla nts. Here we describe three instability determinants in the termini of the cauliflower mosaic virus (CaMV) capsid protein precursor, of which one is s till present in the mature capsid protein p44. A modified ubiquitin protein reference technique was used to show that these motifs are still active wh en fused to a heterologous reporter gene. The N-terminus of p44 contains a degradation motif characterized by proline, glutamate, aspartate, serine an d threonine residues (PEST), which can be inactivated by mutation of three glutamic acid residues to alanines. The signals from the precursor do not c orrespond to known degradation motifs, although they confer high instabilit y on proteins expressed in plant protoplasts. All three instability determi nants were also active in mammalian cells. The PEST signal had a significan tly higher degradation activity in HeLa cells, whereas the precursor signal s 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.