RESUMO
BACKGROUND: 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. 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. RESULTS: Here, 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. CONCLUSIONS: The 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.
Assuntos
Evolução Molecular , Proteínas de Plantas/genética , Plantas/genética , Complexos Ubiquitina-Proteína Ligase/genética , Sequência de Aminoácidos , Ciclossomo-Complexo Promotor de Anáfase , Arabidopsis/genética , Sequência de Bases , Clorófitas/enzimologia , Clorófitas/genética , Mapeamento Cromossômico , Cromossomos de Plantas/genética , Regulação da Expressão Gênica de Plantas , Variação Genética , Genoma de Planta/genética , Dados de Sequência Molecular , Oryza/genética , Filogenia , Proteínas de Plantas/classificação , Plantas/enzimologia , Populus/genética , Subunidades Proteicas/classificação , Subunidades Proteicas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Rodófitas/enzimologia , Rodófitas/genética , Especificidade da Espécie , Sintenia , Complexos Ubiquitina-Proteína Ligase/classificaçãoRESUMO
BACKGROUND: The patterns of emergence and diversification of the families of ubiquitin ligases provide insights about the evolution of the eukaryotic ubiquitination system. U-box ubiquitin ligases (UULs) are proteins characterized by containing a peculiar protein domain known as U box. In this study, the origin of the animal UUL genes is described. RESULTS: Phylogenetic and structural data indicate that six of the seven main UUL-encoding genes found in humans (UBE4A, UBE4B, UIP5, PRP19, CHIP and CYC4) were already present in the ancestor of all current metazoans and the seventh (WDSUB1) is found in placozoans, cnidarians and bilaterians. The fact that only 4-5 genes orthologous to the human ones are present in the choanoflagellate Monosiga brevicollis suggests that several animal-specific cooptions of the U box to generate new genes occurred. Significantly, Monosiga contains five additional UUL genes that are not present in animals. One of them is also present in distantly-related protozoans. Along animal evolution, losses of UUL-encoding genes are rare, except in nematodes, which lack three of them. These general patterns are highly congruent with those found for other two families (RBR, HECT) of ubiquitin ligases. CONCLUSIONS: Finding that the patterns of emergence, diversification and loss of three unrelated families of ubiquitin ligases (RBR, HECT and U-box) are parallel indicates that there are underlying, linage-specific evolutionary forces shaping the complexity of the animal ubiquitin system.
