Abstract
BackgroundThe orderly progression through mitosis is regulated by the Anaphase-Promoting Complex (APC), a large multiprotein E3 ubiquitin ligase that targets key cell-cycle regulators for destruction by the 26 S proteasome. The APC is composed of at least 11 subunits and associates with additional regulatory activators during mitosis and interphase cycles. Despite extensive research on APC and activator functions in the cell cycle, only a few components have been functionally characterized in plants.ResultsHere, we describe an in-depth search for APC subunits and activator genes in the Arabidopsis, rice and poplar genomes. Also, searches in other genomes that are not completely sequenced were performed. Phylogenetic analyses indicate that some APC subunits and activator genes have experienced gene duplication events in plants, in contrast to animals. Expression patterns of paralog subunits and activators in rice could indicate that this duplication, rather than complete redundancy, could reflect initial specialization steps. The absence of subunit APC7 from the genome of some green algae species and as well as from early metazoan lineages, could mean that APC7 is not required for APC function in unicellular organisms and it may be a result of duplication of another tetratricopeptide (TPR) subunit. Analyses of TPR evolution suggest that duplications of subunits started from the central domains.ConclusionsThe increased complexity of the APC gene structure, tied to the diversification of expression paths, suggests that land plants developed sophisticated mechanisms of APC regulation to cope with the sedentary life style and its associated environmental exposures.
Highlights
The orderly progression through mitosis is regulated by the Anaphase-Promoting Complex (APC), a large multiprotein E3 ubiquitin ligase that targets key cell-cycle regulators for destruction by the 26 S proteasome
Identification of APC subunits and activator genes In order to carry out the cross-species comparison of the APC and activators, we have searched for homologous sequences in the Genomic Research (TIGR) Rice genome database and DOE Join Genome Institute (JGI) Poplar genome database
The two isoforms of CDC23 and APC11 genes in rice are differentially expressed in light-dark grown plants and one of APC11 subunits is more expressed in the inflorescence than the other
Summary
The orderly progression through mitosis is regulated by the Anaphase-Promoting Complex (APC), a large multiprotein E3 ubiquitin ligase that targets key cell-cycle regulators for destruction by the 26 S proteasome. An irreversible mechanism of CDK down-regulation is destruction of cyclin subunits [2,3]. At the G1- to S-phase and metaphase to anaphase transitions, CDKs are irreversibly inactivated by ubiquitin-mediated proteolysis of cognate cyclins [4]. Degradation of protein substrates through the ubiquitin-proteasome pathway involves the activity of different E3 ligases, among them the anaphase-. Other targets of APC/C degradation are: Cyclins A and B; protein kinases Plk, CDC5, Aurora A and B; regulators of DNA replication Geminin, CDC6; and the anaphase inhibitor Securin (reviewed in [17]). The proteolytic events triggered by the APC are required to release sister chromatides cohesion during anaphase, to control the exit from mitosis and to prevent premature entry into S-phase [6,18,19]
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