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: 2310

#Unit 3. Fundamental Processes

The transition from the closed to the open complex involves structural changes in the enzyme and the opening of the DNA double helix to reveal the template and nontemplate strands. This “melting” occurs between positions –11 and +2, with respect to the transcription start site.

TLS Online TPP Program

#Id: 712

#Unit 3. Fundamental Processes

Hda is recruited by DNA Polymerase in previous cycle and it acts to switch off DnaA, preventing a second round of replication.

TLS Online TPP Program

#Id: 10035

#Unit 4. Cell Communication and Cell Signaling

NF-κB signaling is turned off by negative feedback

regulation because one of the genes whose transcription is induced by NF-κB encodes I-κBα.

TLS Online TPP Program

#Id: 5063

#Unit 3. Fundamental Processes

Replication in bacteria and in eukaryotes is licensed and permitted to occur only once per cell cycle. Each replicon is allowed to fire only once.

TLS Online TPP Program

#Id: 9682

#Unit 4. Cell Communication and Cell Signaling

PTEN can remove phosphate groups attached to serine,

threonine, and tyrosine residues in proteins, its ability to

remove the 3-phosphate from PI(3,4,5)P3 is its major function in cells.