A role of p73 in mitotic exit.
The p53-related p73 proteins regulate developmental processes, cell growth, and DNA damage response. p73 function is regulated by post-translational modifications and protein-protein interactions. At the G2/M transition, p73 is phosphorylated at Thr-86 by the p34cdc2/cyclin B complex; this is associated with its exclusion from condensed chromosomes and loss of DNA binding and transcriptional activation ability. Here we showed that p73 hypo-phosphorylated species reappear during mitotic exit, concomitant with p73 relocalization to telophase nuclei and recovered ability to activate transcription. Functional knock-out of p73 gene expression by small interfering RNAs (siRNAs) alters mitotic progression, yielding an increase of ana-telophase cells, the accumulation of aberrant late mitotic figures, and the appearance of abnormalities in the subsequent interphase. This p73 activity at the M-to-G1 transition is mediated by its transactivating function because expression of the transcription dominant negative mutant p73DD induces the same mitotic exit phenotype. We also found that the cyclin-dependent kinase inhibitor Kip2/p57 gene is a specific target of p73 regulation during mitotic exit and re-entry into G1. Both knock-out of p73 gene expression by siRNAs and abrogation of p73-dependent transcription by the p73DD mutant abrogate Kip2/p57 increase at the M-to-G1 transition. Moreover, similar abnormalities (e.g. delay in late mitotic stages with the accumulation of aberrant ana-telophase figures, and abnormalities in the following interphase) are observed in cultures in which the expression of Kip2/p57 is abrogated by siRNAs. These results identify a novel p73-Kip2/p57 pathway that coordinates mitotic exit and transition to G1.
Laboratory of Gene Expression, Fondazione Andrea Cesalpino, 00161 Rome Italy.
Paola
P
Merlo
Marcella
M
Fulco
Antonio
A
Costanzo
Rosamaria
R
Mangiacasale
Sabrina
S
Strano
Giovanni
G
Blandino
Yoichi
Y
Taya
Patrizia
P
Lavia
Massimo
M
Levrero
D000705:Anaphase; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002469:Cell Separation; D002875:Chromosomes / Q000648:ultrastructure; D019926:Cyclin B / Q000378:metabolism; D050761:Cyclin-Dependent Kinase Inhibitor p57; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D005434:Flow Cytometry; D016193:G1 Phase; D005799:Genes, Dominant; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D005910:Glioma / Q000378:metabolism; D006801:Humans; D008938:Mitosis; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D010641:Phenotype; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013692:Telophase; D013912:Threonine / Q000737:chemistry; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins
C493964:CDKN1C protein, human; D019926:Cyclin B; D050761:Cyclin-Dependent Kinase Inhibitor p57; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D013912:Threonine; D012313:RNA; D016203:CDC2 Protein Kinase