Intermolecular DNA interactions stimulated by the cohesin complex in vitro: implications for sister chromatid cohesion.
The establishment of sister chromatid cohesion during S phase and its dissolution at the metaphase-anaphase transition are essential for the faithful segregation of chromosomes in mitosis [1-4]. Recent studies in yeast genetics and Xenopus biochemistry have identified a large protein complex, cohesin, that plays a key role in sister chromatid cohesion [5-10]. The cohesin complex consists of a heterodimeric pair of SMC (structural maintenance of chromosomes) subunits and at least two non-SMC subunits. This structural organization is reminiscent of that of condensin, another major SMC protein complex that drives chromosome condensation in eukaryotic cells [11]. Condensin has been shown to reconfigure and compact DNA in vitro by utilizing the energy of ATP hydrolysis [12]. Very little is known, however, about how cohesin works at a mechanistic level. Here we report the first set of biochemical activities associated with an intact cohesin complex purified from HeLa cell extracts. The cohesin complex binds directly to double-stranded DNA and induces the formation of large protein-DNA aggregates. In the presence of topoisomerase II, cohesin stimulates intermolecular catenation of circular DNA molecules. This activity is in striking contrast to intramolecular knotting directed by condensin [13]. Cohesin also increases the probability of intermolecular ligation of linear DNA molecules in the presence of DNA ligase. Our results are consistent with a model in which cohesin functions as an intermolecular DNA crosslinker and is part of the molecular "glue" that holds sister chromatids together [14].
Losada
A
A
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Hirano
T
T
D000251:Adenosine Triphosphatases / Q000302:isolation & purification / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D018797:Cell Cycle Proteins; D002842:Chromatids / Q000502:physiology*; D002868:Chromosomal Proteins, Non-Histone; D004247:DNA / Q000378:metabolism*; D011088:DNA Ligases / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism; D005656:Fungal Proteins; D006367:HeLa Cells; D006801:Humans; D046912:Multiprotein Complexes; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D014982:Xenopus laevis; D000097722:Cohesins
D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004247:DNA; D011088:DNA Ligases; D004270:DNA, Circular; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D000097722:Cohesins; C108312:condensin complexes