Smad7 binds to the activated RI receptors and blocks its ability to phosphorylate Smad2 or Smad3. 

TLS Online TPP Program

#Id: 8855

#XL - T Zoology

Cohesins are composed of four subunits: 

Smc1, Smc3, Scc1, and Scc3

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#Id: 8856

#XL - T Zoology

Smc1 and Smc3 are members of the structural

maintenance of chromosomes (SMC) protein family, characterized by globular domains at the N- & C-termini connected by a long α helix, bind and hydrolyze ATP.

TLS Online TPP Program

#Id: 8857

#XL - T Zoology

The ATPase domains interact with the proteins

Scc1 and Scc3, which together form a cohesin ring structure which embrace one or both copies of the replicated DNA.

TLS Online TPP Program

#Id: 8858

#XL - T Zoology

Cohesin-mediated cohesion between sister chromatids is established by a two-step process:

1.Loading and unloading of cohesins

2. Stabilization of cohesins

TLS Online TPP Program

#Id: 8859

#XL - T Zoology

During G1, 

cohesins associate with chromosomes by cohesin loading factors Scc2 and Scc4 and unloaded continuously by a cohesin associated complex Pds5 and Wap1 proteins. 

TLS Online TPP Program

#Id: 8860

#XL - T Zoology

During S phase

DNA-bound G1 cohesins Convert into cohesive complexes by cohesin acetyl transferases (CoATs)

which acetylate Smc3 subunit & prevents unloading of cohesins by Pds5-Wapl, thereby stabilizing the cohesins on chromosomes.