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RAD50, an SMC family member with multiple roles in DNA break repair: how does ATP affect function?

Kinoshita E, van der Linden E, Sanchez H, Wyman C - Chromosome Res. (2009)

Bottom Line: All current evidence indicates that ATP binding and hydrolysis cause architectural rearrangements in SMC protein complexes that are important for their functions in organizing DNA.In the case of the MRN complex, the functional significance of ATP binding and hydrolysis are not yet defined.We present some speculation on the role of ATP for function of the MRN complex based on the similarities and differences in the molecular architecture of the Rad50-containing complexes and the SMC complexes condensin and cohesin.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Genetics, Erasmus University Medical Center, Box 2040, 3000 CA Rotterdam, The Netherlands.

ABSTRACT
The protein complex including Mre11, Rad50, and Nbs1 (MRN) functions in DNA double-strand break repair to recognize and process DNA ends as well as signal for cell cycle arrest. Amino acid sequence similarity and overall architecture make Rad50 a member of the structural maintenance of chromosome (SMC) protein family. Like SMC proteins, Rad50 function depends on ATP binding and hydrolysis. All current evidence indicates that ATP binding and hydrolysis cause architectural rearrangements in SMC protein complexes that are important for their functions in organizing DNA. In the case of the MRN complex, the functional significance of ATP binding and hydrolysis are not yet defined. Here we review the data on the ATP-dependent activities of MRN and their possible mechanistic significance. We present some speculation on the role of ATP for function of the MRN complex based on the similarities and differences in the molecular architecture of the Rad50-containing complexes and the SMC complexes condensin and cohesin.

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Scanning force microscopy images of purified human MR and MRN complexes. The large globular domain including the Rad50 ATPase heads, Mre11 and Nbs1, if present, is the high darker colored object from which the two 50 nm long coiled coils protrude. The top two images are MRN and the bottom two images are MR. The hook domains are not stable as the ‘closed’ (left images) and ‘open’ (right images) conformations are about equally prevalent. These approximately 100 nm×100 nm images are presented as tilted views to emphasize topography, color indicates height from 0 to 4 nm (red to purple)
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Figure 4: Scanning force microscopy images of purified human MR and MRN complexes. The large globular domain including the Rad50 ATPase heads, Mre11 and Nbs1, if present, is the high darker colored object from which the two 50 nm long coiled coils protrude. The top two images are MRN and the bottom two images are MR. The hook domains are not stable as the ‘closed’ (left images) and ‘open’ (right images) conformations are about equally prevalent. These approximately 100 nm×100 nm images are presented as tilted views to emphasize topography, color indicates height from 0 to 4 nm (red to purple)

Mentions: Some speculation on the role of ATP in DNA binding and function can be considered on the basis of the similarities and differences in the molecular architecture of Rad50 complex, condensin, and cohesin (Fig. 2). Rad50 and the other SMC proteins have in common a very elongated overall structure due to an extended amino acid region encoding a coiled coil, up to 50 nm long. At one end of this elongated coiled coil, the juxtaposed N- and C-terminal domains form a functional ATPase. The other end of the coiled coil, the apex where the amino acid sequence turns back on itself, can be described in all of these proteins as an interaction domain (Fig. 2a). Rad50, condensin, and cohesin are all arranged in dimeric complexes of two elongated structures. The manner in which the elongated coiled-coil structures are connected and the resulting disposition of the ATPase domains differ between Rad50 and the SMCs cohesin and condensin (Fig. 2b). Cohesin and condensin dimerize by a stable interface at the globular ‘hinge’ domains located at the coiled-coil apex. This places the ATPase domains of the SMCs tethered at the ends of two long (and possibly flexible) coiled coils. In contrast, the smaller CxxC amino acid motif at the Rad50 coiled-coil apex is not a stable dimerization domain (Fig. 4). Two Rad50s are included in complexes by interaction with Mre11, which is a stable dimer alone and binds Rad50 along the coiled coils near the ATPase domain (Hopfner et al. 2001). Cohesin and condensin function together with partner proteins that interact at or near the ATPase domains. Inclusion of the SMC partner proteins in complexes modulates association of the ATPase domains and or ATPase activity, and can result in a ring-like structure in which both ends of the coiled coils are attached via protein–protein interactions (Haering et al. 2008). Rad50 functions together with Mre11, which defines the dimer interactions, and sometimes with Nbs1 in a yet undefined arrangement and stoichiometry.


RAD50, an SMC family member with multiple roles in DNA break repair: how does ATP affect function?

Kinoshita E, van der Linden E, Sanchez H, Wyman C - Chromosome Res. (2009)

Scanning force microscopy images of purified human MR and MRN complexes. The large globular domain including the Rad50 ATPase heads, Mre11 and Nbs1, if present, is the high darker colored object from which the two 50 nm long coiled coils protrude. The top two images are MRN and the bottom two images are MR. The hook domains are not stable as the ‘closed’ (left images) and ‘open’ (right images) conformations are about equally prevalent. These approximately 100 nm×100 nm images are presented as tilted views to emphasize topography, color indicates height from 0 to 4 nm (red to purple)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494100&req=5

Figure 4: Scanning force microscopy images of purified human MR and MRN complexes. The large globular domain including the Rad50 ATPase heads, Mre11 and Nbs1, if present, is the high darker colored object from which the two 50 nm long coiled coils protrude. The top two images are MRN and the bottom two images are MR. The hook domains are not stable as the ‘closed’ (left images) and ‘open’ (right images) conformations are about equally prevalent. These approximately 100 nm×100 nm images are presented as tilted views to emphasize topography, color indicates height from 0 to 4 nm (red to purple)
Mentions: Some speculation on the role of ATP in DNA binding and function can be considered on the basis of the similarities and differences in the molecular architecture of Rad50 complex, condensin, and cohesin (Fig. 2). Rad50 and the other SMC proteins have in common a very elongated overall structure due to an extended amino acid region encoding a coiled coil, up to 50 nm long. At one end of this elongated coiled coil, the juxtaposed N- and C-terminal domains form a functional ATPase. The other end of the coiled coil, the apex where the amino acid sequence turns back on itself, can be described in all of these proteins as an interaction domain (Fig. 2a). Rad50, condensin, and cohesin are all arranged in dimeric complexes of two elongated structures. The manner in which the elongated coiled-coil structures are connected and the resulting disposition of the ATPase domains differ between Rad50 and the SMCs cohesin and condensin (Fig. 2b). Cohesin and condensin dimerize by a stable interface at the globular ‘hinge’ domains located at the coiled-coil apex. This places the ATPase domains of the SMCs tethered at the ends of two long (and possibly flexible) coiled coils. In contrast, the smaller CxxC amino acid motif at the Rad50 coiled-coil apex is not a stable dimerization domain (Fig. 4). Two Rad50s are included in complexes by interaction with Mre11, which is a stable dimer alone and binds Rad50 along the coiled coils near the ATPase domain (Hopfner et al. 2001). Cohesin and condensin function together with partner proteins that interact at or near the ATPase domains. Inclusion of the SMC partner proteins in complexes modulates association of the ATPase domains and or ATPase activity, and can result in a ring-like structure in which both ends of the coiled coils are attached via protein–protein interactions (Haering et al. 2008). Rad50 functions together with Mre11, which defines the dimer interactions, and sometimes with Nbs1 in a yet undefined arrangement and stoichiometry.

Bottom Line: All current evidence indicates that ATP binding and hydrolysis cause architectural rearrangements in SMC protein complexes that are important for their functions in organizing DNA.In the case of the MRN complex, the functional significance of ATP binding and hydrolysis are not yet defined.We present some speculation on the role of ATP for function of the MRN complex based on the similarities and differences in the molecular architecture of the Rad50-containing complexes and the SMC complexes condensin and cohesin.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Genetics, Erasmus University Medical Center, Box 2040, 3000 CA Rotterdam, The Netherlands.

ABSTRACT
The protein complex including Mre11, Rad50, and Nbs1 (MRN) functions in DNA double-strand break repair to recognize and process DNA ends as well as signal for cell cycle arrest. Amino acid sequence similarity and overall architecture make Rad50 a member of the structural maintenance of chromosome (SMC) protein family. Like SMC proteins, Rad50 function depends on ATP binding and hydrolysis. All current evidence indicates that ATP binding and hydrolysis cause architectural rearrangements in SMC protein complexes that are important for their functions in organizing DNA. In the case of the MRN complex, the functional significance of ATP binding and hydrolysis are not yet defined. Here we review the data on the ATP-dependent activities of MRN and their possible mechanistic significance. We present some speculation on the role of ATP for function of the MRN complex based on the similarities and differences in the molecular architecture of the Rad50-containing complexes and the SMC complexes condensin and cohesin.

Show MeSH
Related in: MedlinePlus