Nearest neighbour analysis of MCM protein complexes in Drosophila melanogaster.
The MCM proteins are a group of six proteins whose action is vital for DNA replication in eukaryotes. It has been suggested that they constitute the replicative helicase, with a subset of the proteins forming the catalytic helicase (MCM4,6,7) while the others have a loading or control function. In this paper we show that all six MCM proteins are present in equivalent amounts in soluble extracts and on chromatin. We have also analysed soluble and chromatin-associated MCM protein complexes under different conditions. This suggests that all six MCM proteins are always found in a complex with each other, although the interaction between the individual MCM proteins is not equivalent as stringent salt conditions are able to break the intact complex into a number of stable subcomplexes. These data contribute to the ongoing debate about the nature of MCM complexes, supporting the hypothesis that they act as a heterohexamer rather than as a number of different subcomplexes. Finally, using protein-protein cross-linking we have shown that MCM2 interacts directly with MCM5 and MCM6; MCM5 with MCM3 and MCM2; and MCM6 with MCM2 and MCM4. This provides the first direct information about specific subunit contacts in the MCM complex.
Crevel
G
G
Department of Biochemistry, St Georges Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK.
Ivetic
A
A
Ohno
K
K
Yamaguchi
M
M
Cotterill
S
S
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002457:Cell Extracts / Q000032:analysis; D002458:Cell Fractionation; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D003432:Cross-Linking Reagents / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D046911:Macromolecular Substances; D064148:Minichromosome Maintenance Complex Component 4; D064151:Minichromosome Maintenance Complex Component 6; D064168:Minichromosome Maintenance Complex Component 7; D009687:Nuclear Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D013388:Succinimides / Q000737:chemistry
D018797:Cell Cycle Proteins; D002457:Cell Extracts; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D046911:Macromolecular Substances; C491087:Mcm7 protein, Drosophila; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D013388:Succinimides; C085711:mcm5 protein, S pombe; C092802:MCM4 protein, S cerevisiae; C491207:MCM6 protein, S cerevisiae; C491088:MCM7 protein, S cerevisiae; C491204:Mcm6 protein, Drosophila; D064148:Minichromosome Maintenance Complex Component 4; D064151:Minichromosome Maintenance Complex Component 6; D064168:Minichromosome Maintenance Complex Component 7; C011240:dithiobis(succinimidylpropionate)