Both negative and positive G1 cell cycle regulators undergo proteasome-dependent degradation during sucrose starvation in Arabidopsis.
The proteasome pathway regulates many aspects of biological processes in plants, such as plant hormone signaling, light responses, the circadian clock and regulation of cell division. Key cell-cycle regulatory proteins including B-type cyclins, Cdc6, cyclin-dependent kinase inhibitors and E2Fc undergo proteasome-dependent degradation. We used the proteasome inhibitor MG132 to show that proteolysis of Arabidopsis RETINOBLASTOMA-RELATED 1 (AtRBR1) and three E2Fs is mediated by the proteasome pathway during sucrose starvation in Arabidopsis suspension MM2d cells. We found previously that estrogen-inducible RNAi-mediated downregulation of AtRBR1 leads to a higher frequency of arrest in G2 phase, instead of G1-phase arrest in the uninduced control, after sucrose starvation. Degradation of not only negative (AtRBR1 and E2Fc) but also positive (E2Fa and E2Fb) cell cycle regulators after sucrose starvation may be required for arrest in G1 phase, when cells integrate a variety of nutritional, hormonal and developmental signals to decide whether or not to commit to entry into the cell cycle.
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan.
Hiroto
H
Hirano
Atsuhiko
A
Shinmyo
Masami
M
Sekine
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
D029681:Arabidopsis Proteins; D050684:E2F Transcription Factors; C514752:E2FC protein, Arabidopsis; C496141:E2Fa protein, Arabidopsis; C506682:E2Fb protein, Arabidopsis; C487568:RBR1 protein, Arabidopsis; D013395:Sucrose; D046988:Proteasome Endopeptidase Complex