Philip Renshaw | PubMed Health

PubMed2006

Structural diversity in p160/CREB-binding protein coactivator complexes.

Ligand-induced transcription by nuclear receptors involves the recruitment of p160 coactivators such as steroid receptor coactivator 1 (SRC1), in complex with histone acetyltransferases such as CREB-binding protein (CBP) and p300. Here we describe the solution structure of a complex formed by the SRC1 interaction domain (SID) of CBP and the activation domain (AD1) of SRC1, both of which contain four helical regions (Calpha1, Calpha2, Calpha3, and Calpha3' in CBP and Salpha1, Salpha2', Salpha2, and Salpha3 in SRC1). A tight four-helix bundle is formed between Salpha1, Calpha1, Calpha2, and Calpha3 that is capped by Salpha3. In contrast to the structure of the AD1 domain of the related p160 protein ACTR in complex with CBP SID, the sequences forming Salpha2' and Salpha2 in SRC1 AD1 are not involved in the interface between the two domains but rather serve to position Salpha3. Thus, although the CBP SID domain adopts a similar fold in complex with different p160 proteins, the topologies of the AD1 domains are strikingly different, a feature that is likely to contribute to functional specificity of these coactivator complexes.

Amino Acid Sequence↗

PubMed2005

Superior T cell activation by ESAT-6 as compared with the ESAT-6-CFP-10 complex.

Using intracellular cytokine staining we show herein that T cells will respond to short-term (6 h) activation with phorbol ester plus ionomycin by production of tumor necrosis factor (TNF), IFN-gamma or both. Here CD4 T cells preferentially produce TNF and CD8 cells IFN-gamma. The same pattern is seen when T cells are activated with the Mycobacterium tuberculosis protein early secretory antigenic target-6 (ESAT-6). Responses with >0.02% IFN-gamma+ CD3 cells were seen in 8 of 10 patients diagnosed with tuberculosis and in 12 of 14 healthy individuals selected for likely exposure to M. tuberculosis. T cell responses to the 1:1 complex of ESAT-6 and culture filtrate protein-10 (CFP-10) were inferior to ESAT-6 alone, and only reached the level of T cell response achieved with CFP-10 alone. Extending the time of incubation to 18 h leads to an increased response to the complex, but it still reached only the level of CFP-10 alone. In vitro digestion with lysosomal enzymes cathepsin L and S at 2000:1 protein to enzyme ratio demonstrates rapid digestion of the individual proteins while the ESAT-6-CFP-10 complex is resistant. The data suggest that the natural complex of ESAT-6-CFP-10 is less amenable to antigen processing leading to a lower T cell response as compared with the individual proteins.

Antigen Presentation↗