Dag

Transcriptional activation domain

DNA binding domain

Transcriptional activation domain

Exterior

Cytosol

DNA binding domain

M FIGURE 13-31 Activation of the Tubby transcription factor following ligand binding to receptors coupled to Go or

Gq. In resting cells, Tubby is bound tightly to PIP2 in the plasma membrane. Receptor stimulation (not shown) leads to activation of phospholipase C, hydrolysis of PIP2, and release of Tubby into the cytosol (1). Directed by two functional nuclear localization sequences (NLS) in its N-terminal domain, Tubby translocates into the nucleus (2) and activates transcription of target genes (3). It is not known whether IP3 remains bound to Tubby. [Adapted from S. Santagata et al., 2001, Science 292:2041.]

Nucleus

Transcription

Nucleus

Transcription

► FIGURE 13-32 Activation of gene expression following ligand binding to Gs protein-coupled receptors. Receptor stimulation (1) leads to activation of PKA (2). Catalytic subunits of PKA translocate to the nucleus (3) and there phosphorylate and activate the transcription factor CREB (4). Phosphorylated CREB associates with the co-activator CBP/P300 (5) to stimulate various target genes controlled by the CRE regulatory element. See the text for details. [See K. A. Lee and N. Masson, 1993, Biochim. Biophys. Acta 1174:221, and D. Parker et al., 1996, Mol. Cell Biol. 16(2):694.]

Gs protein-coupled

Exterior receptor Ü

Adenylyl cyclase

Cytosol

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