Two Mechanisms Down-Regulate Signaling from RTKs

1. Phosphotyrosine phosphatases

2. Receptor-mediated endocytosis followed by degradation in lysosomes

TLS Online TPP Program

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#XL - T Zoology

Labile factors called cyclins drive the progression of cells through different stages of the cell cycle by binding to CDKs.

TLS Online TPP Program

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#XL - T Zoology

Cells commit to a new cell division at a specific point in G1 known as START or the restriction point.

TLS Online TPP Program

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#XL - T Zoology

R-factor 

In mammalian cells - cyclin D 

In yeast - Cln3

TLS Online TPP Program

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#XL - T Zoology

TLS Online TPP Program

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#XL - T Zoology

cyclin-CDK complexes preferentially phosphorylate

serine and threonine residues when they are found within the consensus sequence:

[S/T]PX[R/K]K 

TLS Online TPP Program

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#XL - T Zoology

G1 Cyclin–CDKs

In human - cyclin D-CDK 4 

cyclin D-CDK 6

In budding yeast - CIn 3-Cdc 28