A Lin-9 complex is recruited by B-Myb to activate transcription of G2/M genes in undifferentiated embryonal carcinoma cells.
It has recently been discovered that cell-cycle gene transcription is regulated by a core complex named LINC that switches from a transcriptionally repressive complex in G(0)-G(1) with the p130 or p107 pocket proteins and E2F4 to a transcriptionally active complex in S-G(2) containing B-Myb. We have studied the function of LINC in F9 embryonal carcinoma cells, which are distinguished by a rapid cell cycle resulting from an extremely short G(1) phase. We show that suppressing expression of the LINC component, Lin-9, in F9 cells causes arrest in mitosis, and we have used this system to screen for transcriptional targets. In these cells, B-Myb was found in complexes with Lin-9 and several other LINC constituents, however, the pocket proteins did not associate with LINC unless F9 cells were differentiated. Lin-9 and B-Myb were both required for transcription of G(2)/M genes such as Cyclin B1 and Survivin. Moreover, B-Myb was demonstrated to recruit Lin-9 to the Survivin promoter through multiple Myb-binding sites. The demonstration that a B-Myb/LINC complex is vital for progression through mitosis in cells lacking a G(1)/S checkpoint has implications for both undifferentiated embryonal cells and for cancers in which pocket protein function is compromised.
Knight
A S
AS
Department of Virology, Faculty of Medicine, Imperial College London, London, UK.
Notaridou
M
M
Watson
R J
RJ
D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000502:physiology*; D002455:Cell Division / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D019926:Cyclin B / Q000235:genetics; D056744:Cyclin B1; D050684:E2F Transcription Factors / Q000502:physiology; D054278:Embryonal Carcinoma Stem Cells / Q000378:metabolism*; D016195:G2 Phase / Q000235:genetics*; D051034:Inhibitor of Apoptosis Proteins; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins; D000077022:Survivin; D015534:Trans-Activators / Q000502:physiology*; D015533:Transcriptional Activation; D025521:Tumor Suppressor Proteins / Q000502:physiology*
C117749:Birc5 protein, mouse; C534700:Ccnb1 protein, mouse; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D050684:E2F Transcription Factors; D051034:Inhibitor of Apoptosis Proteins; C512498:LIN-9 protein, mouse; D008869:Microtubule-Associated Proteins; C499306:Mybl2 protein, mouse; D012097:Repressor Proteins; D000077022:Survivin; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins