The H3.H4 tetramer forms the top half of the histone octamer. Histone H3.H4 tetramers occupy a key position in the nucleosome by binding the middle and both ends of the DNA

TLS Online TPP Program

#Id: 9469

#Unit 4. Cell Communication and Cell Signaling

IL-2 receptor complex activates

STATs 1, 3, and 5 but not STATs 2 or 4

TLS Online TPP Program

#Id: 9470

#Unit 4. Cell Communication and Cell Signaling

Phosphorylated STAT dissociates spontaneously from the receptor, and two phosphorylated STAT proteins form a homodimer.

TLS Online TPP Program

#Id: 9471

#Unit 4. Cell Communication and Cell Signaling

STAT5 becomes activated in erythroid progenitor cells and induces expression of the protein Bcl-xL.

TLS Online TPP Program

#Id: 9472

#Unit 4. Cell Communication and Cell Signaling

Two mechanisms for terminating cytokine signaling:

1. Short-term regulation: SHP1

2. Long-term regulation: SOCS proteins

TLS Online TPP Program

#Id: 9473

#Unit 4. Cell Communication and Cell Signaling

SHP1 a phosphotyrosine phosphatase, contains:

SH2 domain  & Phosphatase domain

TLS Online TPP Program

#Id: 9474

#Unit 4. Cell Communication and Cell Signaling

SHP1 

Binding of an SH2 domain to a phosphotyrosine in the activated receptor unmasks its phosphatase catalytic site