The hbrm and BRG-1 proteins, components of the human SNF/SWI complex, are phosphorylated and excluded from the condensed chromosomes during mitosis.
In yeast, the SNF/SWI complex is believed to regulate transcription by locally altering the chromatin structure. At the present time, three human homologues of yeast SNF/SWI proteins have been characterized: hbrm and BRG-1, homologues of SNF2/SWI2, and hSNF5, a homologue of SNF5. We show here that, during mitosis, hbrm and BRG-1 are phosphorylated and excluded from the condensed chromosomes. In this phase of the cell cycle, the level of hbrm protein is also strongly reduced, whereas the level of BRG-1 remains constant. The mitotic phosphorylation of hbrm and BRG-1 is found not to disrupt the association of these proteins with hSNF5 but correlates with a decreased affinity for the nuclear structure in early M phase. We suggest that chromosomal exclusion of the human SNF/SWI complex at the G2-M transition could be part of the mechanism leading to transcriptional arrest during mitosis.
Muchardt
C
C
Unité des Virus Oncogènes, UA1644 du CNRS, Département des Biotechnologies, Institut Pasteur, Paris, France.
Reyes
J C
JC
Bourachot
B
B
Leguoy
E
E
Yaniv
M
M
D000906:Antibodies / Q000276:immunology / Q000302:isolation & purification; D002460:Cell Line; D002877:Chromosomes, Human; D004265:DNA Helicases; D015536:Down-Regulation; D016193:G1 Phase; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D014157:Transcription Factors / Q000276:immunology / Q000378:metabolism*
D000906:Antibodies; D009687:Nuclear Proteins; C084011:SMARCA2 protein, human; D014157:Transcription Factors; C084108:SMARCA4 protein, human; D004265:DNA Helicases