In Meristematic zone, 

cells divide both in the direction of the root base to form cells that will differentiate into the tissues of the functional root and in the direction of the root apex to form the root cap

TLS Online TPP Program

#Id: 8619

#XL - R Botany

INK4s

bind to CDK4 and CDK6 monomers, blocking their interaction with cyclin D

TLS Online TPP Program

#Id: 8620

#XL - R Botany

A second class of CKIs found in metazoan cells is the Cip/Kip family of CKIs, consists of three proteins—p21CIP, p27KIP1, and p57KIP2. 

TLS Online TPP Program

#Id: 8621

#XL - R Botany

The Cip/Kip family members bind to cyclin-bound CDKs and block the activity of cyclin D-, E-, A-, and B-containing complexes.

TLS Online TPP Program

#Id: 8622

#XL - R Botany

Cyclins are degraded through the action of two different E3-ligases:

1. SCF (Skp1, Cullin, and F-box proteins) 

2. APC/C or cyclosome

TLS Online TPP Program

#Id: 8623

#XL - R Botany

SCF and APC/C are multisubunit ubiquitin-protein ligases that belong to the RING finger family of ubiquitin-protein ligases.

TLS Online TPP Program

#Id: 8625

#XL - R Botany

Human SCF complexes contain: 

Three core components - Cul1 subunit, RBX1, Skp1 

and a substrate-targeting F-box protein