Transcription factors continued transcriptional activation

Transcriptional activators. Many proteins serve as activators of transcription, causing larger increases in rate over those observed with TBP alone. Some of these are listed in Table 28-2.338a The table also lists two proteins (Spl and NF1), and the DNA sequence CCAAT, which control constitutive or continuously active genes. A large group of transcription factors are active in development. Receptors may be resident in cytoplasm, cell membrane or nucleus, as indicated in Table 28-2. Some cytoplasmic factors are latent, becorn-... 

Cyclin E also performs its function in Gi/S phase. It demonstrates a periodic concentration change with a maximal value at the start of S phase. Afterwards, its concentration falls off sharply within S phase. The gene for cyclin E is also induced by transcription factor E2F which explains the increase in cyclin E at the Gi/S transition. Cyclin E binds and activates CDK2. The activated CDK2 complex is also involved in phosphorylation of the pRb protein. As a consequence, a signal is transmitted, with cooperation of cyclin D, in the direction of the transcription of genes that are essential for the continuation of the cell cycle. 

Transcription factors are known to be substrates of HATs, whereas the enzymes responsible for the acetylation of nonnuclear proteins in many cases are not well known (55). The number of proteins that are regulated by acetylation will continue to increase as method to detect protein acetylation improves. Acetylation of nonhistone proteins can change protein-protein interaction, regulate enzymatic activity, and increase protein stability by suppressing ubiquitinylation (55). 

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