Related Experiment Videos
Physical and functional interaction between the transcriptional cofactor CBP and the KH domain protein Sam68
Wei Hong1, Ross J Resnick, Carrie Rakowski
1Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA, USA.
Abstract:
CBP is a multifunctional transcriptional cofactor with tumor suppressor activity. The CH3 domain of CBP binds numerous transcription factors and several viral oncoproteins. We identified the Src substrate and RNA-binding protein Sam68 as novel CH3-binding protein. Sam68 binds the CH3 domain in part through a conserved FXD/EXXXL motif that is shared among several CH3-binding proteins, including the adenoviral oncoprotein E1A and the tumor suppressor p53. Sam68 and CBP interact in vivo and colocalize in nuclear sub-domains. Sam68 has potent transcriptional repression activity that is independent of its RNA binding activity, which suggests that RNA processing and regulation of gene expression by Sam68 are separable functions. Consistent with this, CBP did not stimulate the ability of Sam68 to promote Rev response element-containing mRNA export. Interestingly, Sam68 can regulate RNA processing in the absence of a Rev response element, suggesting that Sam68 functions through a novel RNA element. Together, these findings reveal a previously unidentified function for Sam68 as a transcriptional repressor and suggest that Sam68 might link cellular signaling pathways with components of the transcriptional machinery.
Insights
The study identifies Sam68 as a novel transcriptional repressor that interacts with CBP. This finding suggests Sam68 links cellular signaling to gene expression machinery.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cancer Biology
Background:
- CREB-binding protein (CBP) is a crucial transcriptional cofactor with tumor suppressor functions.
- The CH3 domain of CBP is known to bind various transcription factors and viral oncoproteins.
Purpose of the Study:
- To identify novel binding partners of the CBP CH3 domain.
- To investigate the functional relationship between CBP and its newly identified binding partner, Sam68.
Main Methods:
- Co-immunoprecipitation assays to confirm in vivo interaction between Sam68 and CBP.
- Immunofluorescence microscopy to determine subcellular localization of Sam68 and CBP.
- Reporter assays to assess the transcriptional activity of Sam68.
Main Results:
- Sam68, a Src substrate and RNA-binding protein, was identified as a novel CBP CH3-binding protein.
- Sam68 and CBP interact in vivo and co-localize within nuclear sub-domains.
- Sam68 exhibits potent transcriptional repression activity, separable from its RNA-binding function, potentially through a novel RNA element.
Conclusions:
- Sam68 functions as a transcriptional repressor, independent of its RNA-binding capabilities.
- Sam68 may serve as a link between cellular signaling pathways and the transcriptional machinery.
- The interaction between Sam68 and CBP reveals a new regulatory mechanism in gene expression and potentially cancer biology.