Limits...
A handcuff model for the cohesin complex.

Zhang N, Kuznetsov SG, Sharan SK, Li K, Rao PH, Pati D - J. Cell Biol. (2008)

Bottom Line: Several models for the cohesin complex have been proposed, but the one-ring embrace model currently predominates the field.The results show that three of the four human cohesin core subunits (Smc1, Smc3, and Rad21) interact with themselves in an Scc3 (SA1/SA2)-dependent manner.These data support a two-ring handcuff model for the cohesin complex, which is flexible enough to establish and maintain sister chromatid cohesion as well as ensure the fidelity of chromosome segregation in higher eukaryotes.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatric Hematology/Oncology, Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA.

ABSTRACT
The cohesin complex is responsible for the accurate separation of sister chromatids into two daughter cells. Several models for the cohesin complex have been proposed, but the one-ring embrace model currently predominates the field. However, the static configuration of the embrace model is not flexible enough for cohesins to perform their functions during DNA replication, transcription, and DNA repair. We used coimmunoprecipitation, a protein fragment complement assay, and a yeast two-hybrid assay to analyze the protein-protein interactions among cohesin subunits. The results show that three of the four human cohesin core subunits (Smc1, Smc3, and Rad21) interact with themselves in an Scc3 (SA1/SA2)-dependent manner. These data support a two-ring handcuff model for the cohesin complex, which is flexible enough to establish and maintain sister chromatid cohesion as well as ensure the fidelity of chromosome segregation in higher eukaryotes.

Show MeSH

Related in: MedlinePlus

Smc1 and Smc3 coimmunoprecipitate each other as well as themselves. 293T cells were transfected with the appropriate plasmids. After 48 h, cell lysates were prepared and used for IP. The loaded input samples were equivalent to 10% of IP samples. (A) Myc-Smc1 and Myc-Smc3 coimmunoprecipitated endogenous Smc3 and Smc1 as well as endogenous Smc1 and Smc3, respectively. (B and C) Cell lysates were treated with or without DNase I and RNase A before co-IP of Smc1–Smc1 (B) and Smc3–Smc3 (C) was performed. EV, empty vector.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2600748&req=5

fig2: Smc1 and Smc3 coimmunoprecipitate each other as well as themselves. 293T cells were transfected with the appropriate plasmids. After 48 h, cell lysates were prepared and used for IP. The loaded input samples were equivalent to 10% of IP samples. (A) Myc-Smc1 and Myc-Smc3 coimmunoprecipitated endogenous Smc3 and Smc1 as well as endogenous Smc1 and Smc3, respectively. (B and C) Cell lysates were treated with or without DNase I and RNase A before co-IP of Smc1–Smc1 (B) and Smc3–Smc3 (C) was performed. EV, empty vector.

Mentions: Next, we tested whether more than one copy of Smc1 and Smc3 proteins is in the cohesin complex by using a strategy similar to the one used in studying Rad21–Rad21 interaction. It has been previously shown that the cohesin complex contains Smc1 and Smc3 and that they form a heterodimer via their hinge domain (Haering et al., 2002). In the cohesin complex, Smc1 and Smc3 heads are also tethered by Rad21 CT and NT, respectively (Gruber et al., 2003, 2006). In either case, Smc1 and Smc3 proteins should coimmunoprecipitate, and this is confirmed by our data (Fig. 2 A). Our co-IP studies indicated that Myc-Smc1 and Myc-Smc3 also coimmunoprecipitate endogenous Smc1 and Smc3, respectively, which are shown as faint bands under Myc-Smc1 and Myc-Smc3 bands (Fig. 2 A).


A handcuff model for the cohesin complex.

Zhang N, Kuznetsov SG, Sharan SK, Li K, Rao PH, Pati D - J. Cell Biol. (2008)

Smc1 and Smc3 coimmunoprecipitate each other as well as themselves. 293T cells were transfected with the appropriate plasmids. After 48 h, cell lysates were prepared and used for IP. The loaded input samples were equivalent to 10% of IP samples. (A) Myc-Smc1 and Myc-Smc3 coimmunoprecipitated endogenous Smc3 and Smc1 as well as endogenous Smc1 and Smc3, respectively. (B and C) Cell lysates were treated with or without DNase I and RNase A before co-IP of Smc1–Smc1 (B) and Smc3–Smc3 (C) was performed. EV, empty vector.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2600748&req=5

fig2: Smc1 and Smc3 coimmunoprecipitate each other as well as themselves. 293T cells were transfected with the appropriate plasmids. After 48 h, cell lysates were prepared and used for IP. The loaded input samples were equivalent to 10% of IP samples. (A) Myc-Smc1 and Myc-Smc3 coimmunoprecipitated endogenous Smc3 and Smc1 as well as endogenous Smc1 and Smc3, respectively. (B and C) Cell lysates were treated with or without DNase I and RNase A before co-IP of Smc1–Smc1 (B) and Smc3–Smc3 (C) was performed. EV, empty vector.
Mentions: Next, we tested whether more than one copy of Smc1 and Smc3 proteins is in the cohesin complex by using a strategy similar to the one used in studying Rad21–Rad21 interaction. It has been previously shown that the cohesin complex contains Smc1 and Smc3 and that they form a heterodimer via their hinge domain (Haering et al., 2002). In the cohesin complex, Smc1 and Smc3 heads are also tethered by Rad21 CT and NT, respectively (Gruber et al., 2003, 2006). In either case, Smc1 and Smc3 proteins should coimmunoprecipitate, and this is confirmed by our data (Fig. 2 A). Our co-IP studies indicated that Myc-Smc1 and Myc-Smc3 also coimmunoprecipitate endogenous Smc1 and Smc3, respectively, which are shown as faint bands under Myc-Smc1 and Myc-Smc3 bands (Fig. 2 A).

Bottom Line: Several models for the cohesin complex have been proposed, but the one-ring embrace model currently predominates the field.The results show that three of the four human cohesin core subunits (Smc1, Smc3, and Rad21) interact with themselves in an Scc3 (SA1/SA2)-dependent manner.These data support a two-ring handcuff model for the cohesin complex, which is flexible enough to establish and maintain sister chromatid cohesion as well as ensure the fidelity of chromosome segregation in higher eukaryotes.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatric Hematology/Oncology, Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA.

ABSTRACT
The cohesin complex is responsible for the accurate separation of sister chromatids into two daughter cells. Several models for the cohesin complex have been proposed, but the one-ring embrace model currently predominates the field. However, the static configuration of the embrace model is not flexible enough for cohesins to perform their functions during DNA replication, transcription, and DNA repair. We used coimmunoprecipitation, a protein fragment complement assay, and a yeast two-hybrid assay to analyze the protein-protein interactions among cohesin subunits. The results show that three of the four human cohesin core subunits (Smc1, Smc3, and Rad21) interact with themselves in an Scc3 (SA1/SA2)-dependent manner. These data support a two-ring handcuff model for the cohesin complex, which is flexible enough to establish and maintain sister chromatid cohesion as well as ensure the fidelity of chromosome segregation in higher eukaryotes.

Show MeSH
Related in: MedlinePlus