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In vivo association of ATFa with JNK/SAP kinase activities
1Institut de Génétique et de Biologie Moléculaire, INSERM/CNRS/ULP, Strasbourg, France.
Abstract:
The human ATFa proteins belong to the CREB/ATF family of transcription factors. We have previously shown that the ATFa proteins may contribute to the modulation of the transcriptional activity of the Jun/Fos complexes (Chatton et al. (1994). Oncogene, 9, 375-385). We now show that a protein kinase activity is strongly associated with ATFa in vivo, as revealed by coimmunoprecipitation of ATFa/kinase complexes from whole cell extracts, with antibodies against ATFa. Two independent regions were found to be implicated in kinase binding: a major interaction site is located within the N-terminal 82 residues comprising an important metal-chelating element; a weaker binding site corresponds to the basic sequence element preceding the C-terminal leucine-zipper of ATFa. Induction experiments suggest that each of these ATFa domains may interact with different kinases. The major activity is associated with the ATFa N-terminal domain. Based on its response to various inducers, on both in vitro and in vivo binding assays, and on its immunological properties, this activity most likely corresponds to the 54/55 kDa JNK2 protein. Taken together, these observations suggest that the ATFa proteins, among other CREB/ATF proteins, may be important effectors of cell signalling pathways.
Insights
Human ATFa proteins associate with protein kinase activity in vivo. This interaction, primarily involving the N-terminal domain, suggests ATFa proteins are key players in cellular signaling pathways.
Area of Science:
- Molecular Biology
- Cellular Signaling
Background:
- Human ATFa proteins are part of the CREB/ATF transcription factor family.
- Previous research indicated ATFa proteins modulate Jun/Fos complex transcriptional activity.
Purpose of the Study:
- To investigate the in vivo association of protein kinase activity with ATFa proteins.
- To identify the regions of ATFa involved in kinase binding and characterize the associated kinase.
Main Methods:
- Coimmunoprecipitation of ATFa/kinase complexes from whole cell extracts using ATFa antibodies.
- In vitro and in vivo binding assays.
- Analysis of kinase activity response to inducers and immunological properties.
Main Results:
- A significant protein kinase activity was found to be strongly associated with ATFa in vivo.
- Two regions of ATFa were implicated in kinase binding: the N-terminal 82 residues (major site) and a basic sequence element (weaker site).
- The major kinase activity, localized to the ATFa N-terminal domain, was identified as the 54/55 kDa JNK2 protein.
Conclusions:
- ATFa proteins bind to protein kinases, notably JNK2, through distinct domains.
- These interactions suggest ATFa proteins are crucial effectors in cellular signaling pathways.
- ATFa proteins, alongside other CREB/ATF proteins, play a significant role in signal transduction.