Identification of a chromosome-targeting domain in the human condensin subunit CNAP1/hCAP-D2/Eg7.
CNAP1 (hCAP-D2/Eg7) is an essential component of the human condensin complex required for mitotic chromosome condensation. This conserved complex contains a structural maintenance of chromosomes (SMC) family protein heterodimer and three non-SMC subunits. The mechanism underlying condensin targeting to mitotic chromosomes and the role played by the individual condensin components, particularly the non-SMC subunits, are not well understood. We report here characterization of the non-SMC condensin component CNAP1. CNAP1 contains two separate domains required for its stable incorporation into the complex. We found that the carboxyl terminus of CNAP1 possesses a mitotic chromosome-targeting domain that does not require the other condensin components. The same region also contains a functional bipartite nuclear localization signal. A mutant CNAP1 missing this domain, although still incorporated into condensin, was unable to associate with mitotic chromosomes. Successful chromosome targeting of deletion mutants correlated with their ability to directly bind to histones H1 and H3 in vitro. The H3 interaction appears to be mediated through the H3 histone tail, and a subfragment containing the targeting domain was found to interact with histone H3 in vivo. Thus, the CNAP1 C-terminal region defines a novel histone-binding domain that is responsible for targeting CNAP1, and possibly condensin, to mitotic chromosomes.
Department of Biological Chemistry, College of Medicine, University of California, Irvine, California 92697-1700, USA.
Alexander R
AR
Ball
John A
JA
Schmiesing
Changcheng
C
Zhou
Heather C
HC
Gregson
Yoshiaki
Y
Okada
Takefumi
T
Doi
Kyoko
K
Yokomori
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone; D002877:Chromosomes, Human / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006657:Histones / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000075223:Poly-ADP-Ribose Binding Proteins; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D006657:Histones; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D046911:Macromolecular Substances; D046912:Multiprotein Complexes; C413383:NCAPD2 protein, human; D009687:Nuclear Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; C108312:condensin complexes; D049452:Green Fluorescent Proteins; D000251:Adenosine Triphosphatases