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In vivo association of E2F and DP family proteins
C L Wu1, L R Zukerberg, C Ngwu
1Massachusetts General Hospital Cancer Center, Charlestown 02129, USA.
Abstract:
The mammalian transcription factor E2F plays an important role in regulating the expression of genes that are required for passage through the cell cycle. This transcriptional activity is inhibited by association with the retinoblastoma tumor suppressor protein (pRB) or its relatives p107 and p103. The first cDNA from the E2F family to be cloned was designated E2F-1, and multiple E2F family members have now been identified. They bind to DNA as heterodimers, interacting with proteins known as DP. Here we demonstrate that DP is also a family of polypeptides with at least two members (hDP-1 and hDP-2). Both hDP-1 and hDP-2 bind to all E2F family members in vivo, and each complex is capable of activating transcription. However, the various E2F/DP complexes display strong differences in the ability to bind to either pRB or p107 in vivo, and the specificity of pRB or p107 binding is mediated by the E2F subunit.
Insights
The E2F transcription factor regulates cell cycle genes. Researchers found that DP proteins (hDP-1, hDP-2) form heterodimers with E2F, influencing cell cycle progression and binding to tumor suppressor proteins like pRB.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- The E2F transcription factor family is crucial for regulating genes essential for cell cycle progression in mammals.
- E2F activity is negatively regulated by interactions with tumor suppressor proteins, including the retinoblastoma protein (pRB) and its relatives p107 and p103.
Purpose of the Study:
- To investigate the role of DP proteins in E2F transcriptional activity.
- To characterize the interaction between E2F family members and DP proteins (hDP-1, hDP-2).
- To determine how these interactions affect binding to pRB and p107.
Main Methods:
- Cloning of E2F family members and identification of DP protein family members (hDP-1, hDP-2).
- In vivo studies to assess binding between E2F and DP proteins.
- Analysis of transcriptional activation by various E2F/DP complexes.
- In vivo assessment of the binding affinity of E2F/DP complexes to pRB and p107.
Main Results:
- DP is a family of polypeptides, with at least two members: hDP-1 and hDP-2.
- Both hDP-1 and hDP-2 form heterodimers with all identified E2F family members.
- All E2F/DP complexes are capable of activating transcription.
- Significant differences were observed in the in vivo binding of various E2F/DP complexes to pRB and p107.
- The E2F subunit mediates the specificity of pRB and p107 binding.
Conclusions:
- DP proteins are essential partners for E2F transcription factors, forming functional heterodimers.
- The composition of the E2F/DP complex influences its interaction with cell cycle regulatory proteins like pRB and p107.
- These findings elucidate a key mechanism controlling cell cycle gene expression and tumor suppression.