Cell Cycle (CH 19) Flashcards
stages of cell cycle
Gap1, S-phase, Gap 2, Mitosis
Gap 1
cell grows in size, synthesize RNA & proteins needed for DNA synthesis
S-phase
chromosome replication, each copy connects as sister chromatids
Gap 2
cell prepares for mitoses
Mitosis
beginning: nuclear membrane breaks down, retracts to ER, golgi breaks into vesicles, microtubles break down and reassemble into mitotic apparatus, and spindle pole forms and associate with kinetochore
end: sister chromatids move to ends of cell, mitotic spindle disassembles
cyclin
regulatory subunit;
G1 or
B-type (cyclin B&A)- have destruction box w/ APC/C Cdh 1
CDK
cyclin dependent kinase that phosphorylates proteins
Mid G1 cyclin-CDK
activate transcription factors that induce gene expression needed for DNA synthesis and S-phase cyclin and CDKs
(Cyclin D-CDK4 and Cyclin D-CDK6)
Late-G1 cyclin-CDK
phosphorylate inhibitors to activate SCF (ubiquitin protein ligase - leads to inhibition of inhibitors to release S-phase cyclin-CDKs)
(Cyclin E-CDK2)
S-phase cyclin-CDK
phosphorylate proteins, initiate DNA replication, and inhibit reassembly of complexes to ensure single replication
(Cyclin A-CDK2)
Mitotic cyclin-CDK
activated by dephosphorylation; phosphorylates substrates
(Cyclin A-CDK1
Cyclin B - CDK1)
role of Rb and E2F proteins in cell cycle progression
Rb (retinoblastoma) - blocks cell cycle progression by inhibiting activity of E2F transcription factors. Hypophosphorylated Rb binds E2F, blocking it from binding to promoter. In
Mid G1 CyclinD-CDK4/6 phosphorylate Rb. In Late G1: CyclinE-CDK2 hyperphosphorylates Rb, releasing E2F and allowing gene transcription.
E2F regulates expression of genes needed for DNA replication, cyclin-CDKs, etc.
early response genes
induced by transcription factors already present in the cell (CREB, SRF, etc)
late response genes
require new protein synthesis; dependent on transcription and translation of early response genes (include transcription factors & Cyclin-CDKs needed for cell cycle progression)
APC-mediated degradation of mitotic cyclins
Late anaphase:
APC/C is active (bound to Cdh1). APC/C polyubiquitinates mitotic cyclin (A/B) for degragation by proteasome. Kinase activity declines to trigger telophase. G1-cyclin CDK phosphorylates Cdh1, does not associate with APC/C making it inactive.
Prophase:
Mitotic cyclin is synthesized. Cdc14 removes phosphate from Cdh1, allows to activate APC/C.
APC
Anaphase-Promoting Complex
APC promotion of sister chromatid separation
APC, guided and bound by protein Cdc20, ubiquitinates securin. This releases separase to cleave Scc1, allowing sister chromatids (held together at Smc) to dissociate.
cell cycle checkpoints and regulation
Unreplicated DNA: ATR-Chk1
Spindle-assembly: Mad2
Spindle-position: Cdc14
DNA-damage: ATM/R