Rb-E2F complex

Definition

Target type: cellularcomponent

A multiprotein complex containing a heterodimeric E2F transcription factor and a Retinoblastoma (Rb) family member. This complex is capable of repressing transcription of E2F-regulated genes in order to regulate cell cycle progression. [PMID:14616073]

The Rb-E2F complex is a crucial regulatory element in the cell cycle, specifically controlling the transition from the G1 phase to the S phase. This complex is formed by the interaction of the retinoblastoma protein (Rb) and the E2F transcription factor family. Rb is a tumor suppressor protein that acts as a brake on cell cycle progression. It is found primarily in the nucleus and can be localized in the cytoplasm. When Rb is active, it binds to E2F proteins, preventing them from activating genes that are necessary for DNA replication. E2F proteins, in contrast, are transcription factors that activate the expression of genes required for S phase entry.

The Rb-E2F complex can be found in different cellular compartments:

1. **Nucleus:** This is the primary location of the Rb-E2F complex. It is here that Rb interacts with E2F and exerts its inhibitory effect on cell cycle progression. The nuclear localization is essential for Rb to interact with E2F and regulate gene expression.

2. **Cytoplasm:** While the majority of Rb is found in the nucleus, some Rb can also be found in the cytoplasm. The cytoplasmic localization of Rb is not fully understood, but it may play a role in the regulation of Rb levels and its interaction with other cellular factors.

The Rb-E2F complex can be found in different forms depending on the cell cycle phase and the activity of the complex. In the G1 phase, the complex is predominantly active, with Rb bound to E2F. This prevents E2F from activating genes involved in DNA replication. However, as the cell progresses through the G1 phase, signals promoting cell cycle progression activate cyclin-dependent kinases (CDKs). These kinases phosphorylate Rb, leading to its inactivation and the release of E2F. The released E2F can then bind to DNA and activate genes that are necessary for S phase entry.

In summary, the cellular component of the Rb-E2F complex is primarily located in the nucleus, where it interacts with E2F and regulates cell cycle progression. However, Rb can also be found in the cytoplasm, although its exact function in this compartment is not fully understood. The Rb-E2F complex undergoes dynamic changes in its composition and activity throughout the cell cycle, reflecting its crucial role in regulating cell cycle progression.'
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Proteins (1)

Compounds (1)