Depletion of anaphase-promoting complex or cyclosome (APC/C) subunit homolog APC1 or CDC27 of Trypanosoma brucei arrests the procyclic form in metaphase but the bloodstream form in anaphase.
The anaphase-promoting complex or cyclosome (APC/C) is a multiprotein subunit E3 ubiquitin ligase complex that controls segregation of chromosomes and exit from mitosis in eukaryotes. It triggers elimination of key cell cycle regulators such as securin and mitotic cyclins during mitosis by polyubiquitinating them for proteasome degradation. Seven core subunit homologs of APC/C (APC1, APC2, APC11, CDC16, CDC23, CDC27, and DOC1) were identified in the Trypanosoma brucei genome data base. Expression of six of them was individually ablated by RNA interference in both the procyclic and bloodstream forms of T. brucei. Only the CDC27- and APC1-depleted cells were enriched in the G2/M phase with inhibited growth. Further studies indicated that T. brucei APC1 and CDC27 failed to complement the corresponding deletion mutants of budding yeast. However, their depletion from procyclic-form T. brucei enriched cells with two kinetoplasts and an enlarged nucleus possessing short metaphase-like mitotic spindles, suggesting that APC1 and CDC27 may play essential roles in promoting anaphase in the procyclic form. Their depletion from the bloodstream form, however, enriched cells with two kinetoplasts and two nuclei connected through a microtubule bundle, suggesting a late anaphase arrest. This is the first time functional APC/C subunit homologs were identified in T. brucei. The apparent differential activities of this putative APC/C in two distinct developmental stages suggest an unusual function. The apparent lack of functional involvement of some of the other individual structural subunit homologs of APC/C may indicate the structural uniqueness of T. brucei APC/C.
Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-2280, USA.
Praveen
P
Kumar
Ching C
CC
Wang
D000705:Anaphase / Q000502:physiology*; D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome; D064191:Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome; D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D030541:Databases, Genetic; D005434:Flow Cytometry; D018503:Genome, Protozoan; D008677:Metaphase / Q000502:physiology*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D043743:Ubiquitin-Protein Ligase Complexes / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
D064191:Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome; D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; C577441:CDC23 protein, S cerevisiae; C577355:CDC27 protein, S cerevisiae; D018797:Cell Cycle Proteins; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; C577346:APC2 protein, S cerevisiae; D064173:Anaphase-Promoting Complex-Cyclosome; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases