Cell Cycle Control

preparation for DNA replication and growth in cell mass, faithful duplication of the genome, monitoring for damaged DNA and preparation for mitosis, chromosome segregation and division

G1 phase entails _________, S phase entails ______, G2 entails ________, and M phase entails _________.

mid-to-late G1, either progress through the cell cycle or go to G0

The R point is in _______ and is when the cell make the decision to ________

cyclin D accumulates and complexes with Cdk4/6 and CKIs are downregulated

Before the R point…

S phase transcription factors are activated and cyclin E/A accumulate and complex with Cdk2

After the R point…

Centriole duplication, histone synthesis, DNA replication

_____ and ____ occur in S phase, ending with _______.

cyclin D-Cdk4/6

The _____ complex is dominant in G1 and decreases in G2

cyclin E-Cdk2

The _______ complex is dominant in early S phase

cyclin A-Cdk2

The ______ complex is dominant in G2

cyclin B-Cdk1

The ______ complex is dominant at G2-M

serine threonine kinases, inactive as monomers, bound to a cyclin

CDKs are ________ that are ______ and become active when ______

PSTAIRE motif, mediates cyclin binding

A hallmark of the CDK family is the ________, which _______

ATP is in an unfavourable position, T loop blocks the substrate cleft and prevents substrate binding, L12 helix constrains T loop and ATP configuration

In the CDK ground state, ______, ______, and the ______

Reversible phosphorylation

______ regulates cyclin-Cdk kinase activities

conformational change, cyclin packs against PSTAIRE, T loop and STAIRE are pushed in, E51 is rotated and correctly configures ATP, L12 helix melts to a beta sheet, T loop is directed away from the substrate cleft, exposing T161, N and C lobes rotate, T loop and N lobe interaction, Y15 close to the catalytic site, directs substrate to CDK

When cyclin binds CDK, this induces ________ wherein _________, ________, and _______. _______ and ________, allowing substrate binding and ______. _______, preventing ______ and bringing _______. Cyclin then _________.

site of activating phosphorylation and blocks the substrate binding site

The T loop of CDK contains the…

CAK phosphorylates T161 leading to stabilization of T loop position, cyclin binding, T161 phosphorylation

After cyclin binds CDK ________, leading to _______ and ______. ______ leads to further activation.

tyrosine kinase, phosphorylates Y15, inactivate CDK

Wee1 is a ______ that ________, functioning to _______

dual specific kinase, phosphorylates Y15 and T14, inactivate CDK

Myt1 is a _____ that _______, functioning to ______

blocking phosphate transfer

Y15 phosphorylation inactivates CDK by…

blocking ATP binding

T14 phosphorylation inactivates CDK by…

phosphatase, removes phosphate from Y15 and T14, activating cyclin-CDK kinase activity

Cdc25 is a _______ that ________, thus _______.

T14 and Y15, T161

Phosphorylation of _____ inhibits CDKs while phosphorylation of _____ activates CDKs

cyclin proteolysis via ubiquitination, T14 and Y15 phosphorylation by Wee1 and Myt1, and CKI binding

Negative regulation mechanisms of CDKs include:

cyclin binding, T14 and Y15 dephosphorylation by Cdc25, T loop T161 phosphorylation by CAK, and CKI removal

Positive regulation mechanisms of CDKs include:

5, T161 phosphorylation, 100

Cyclin binding leads to conformational change that properly orients ATP for catalysis, resulting in __-fold activation, but _______ is required for full (_____-fold) activation

blocking ATP binding and phosphate transfer

Phosphorylation of T14 and Y15 inhibit CDK activity by…

monomeric CDK, cyclin is bound to CDK

T14 and Y15 are inaccessible in ______ but become exposed when ______

kinase inhibitory protein, CKIs, p21, p27, and p57

The KIP (______) family are a group of _____ including:

inhibitor of CDK4, CKIs, p16, p14, p15, p18

The INK4 (______) family are a group of ____ including:

stoichiometric inhibitors, bind directly to CDK complexes, halt the cell cycle under stress

CKIs are _______ that _______ functioning to ______.

Cip1, all CDKs, p53 dependent, elevated in terminally differentiated cells, quiescence

p21 (aka ____) inhibits ______. Its transcription is ______, expression is ______, and is a marker of _____.

Kip1, all CDKs, sequence homology with p21, induced by TGF-beta and cell-cell contact, elevated in quiescent cells

p27 (aka ____) inhibits _____. It shares ______ and is ______. Expression is ________.

blocking substrate interaction, destabilising ATP binding, and blocking T loop CAK phosphorylation

p21 and p27 block cyclin-Cdk dimer activity by…

Cdk4 and Cdk6, structurally similar, no similarity to Cip/Kip, inhibiting binding of Cdk4/6 to D cyclins

INK4 family members associate with and inhibit _______— family members are _____ and there is ______. They work by…

INK4a, inhibitor of CDK4/6

p16 (aka _____) is an…

14 ARF, 19 ARF, no amino acid similarity

p____ and p_____ are alternate reading frame proteins encoded by p16 locus— they have ______ to p16 or other proteins

INK4b, adjacent to INK4 locus, co-deleted with p16, upregulated by TGF-beta, displaces p27 which is then free to bind cyclin E-Cdk2 to arrest G1

p15 (aka _____) is ______, frequently _____, and _______ (which ______)

INK4 family member predominantly expressed in hematopoietic cells

p18 is a…

cyclin A-Cdk2, binds cyclin groove to block substrate interaction, destabilises ATP binding and binds the T loop to block CAK

p27 binds ______, wherein the N-terminus _______ and the C-terminus _______. Sequence conservation suggests similar mechanisms for p21 and p57.

inserting a peptide arm into the CDK active site thus physically blocking ATP binding and substrate interaction

The Cip/Kip family of CDK inhibitors works by…

Cdk6, opposite from cyclin at the catalytic cleft thus distorting the ATP binding site, attracts T loop and prevents substrate entry and T161 phosphorylation

p19 binds _____, specifically binding ______ which ________. p19 contacts ______ and sequence conservation suggests similar mechanisms for p15, p16, and p18

inhibit Cdk-cyclin binding ad inhibit activity of preassembled complexes

INK4 proteins can both…