The human transcription factors p67SRF and RSRFC4 recognise similar but distinct binding sites which are found in the promoters of both muscle-specific and 'immediate early' genes. Both proteins share a common basic DNA-binding domain, which is defined by the MADS box homology region. The DNA-binding specificity of a truncated form of p67SRF (coreSRF) can be converted to that of RSRFC4. Removal of residues immediately N-terminal to the MADS box relaxes the specificity of coreSRF for its cognate sequence (CC(A/T)6GG) as it improves binding to the RSRFC4 site (CTA(A/T)4TAG). Moreover, the introduction of a single, additional mutation, K154E, into the N-terminal truncated derivative completes the change in specificity to the RSRFC4 binding site. It also influences the salt dependence of DNA binding and ternary complex formation with p62TCF. However, residues at this position do not appear to be involved in direct basepair recognition. These results indicate that although the DNA binding specificity of p67SRF can be converted to that of RSRFC4, the two proteins may bind DNA in different ways. Furthermore, they suggest that binding site specificity can be determined by an indirect mechanism involving residues which are not directly involved in base recognition.
Transcription factors control eukaryotic polymerase II function by influencing the recruitment of multiprotein complexes to promoters and their subsequent integrated function. The complexity of the functional 'transcriptosome' has necessitated biochemical fractionation and subsequent protein sequencing on a grand scale to identify individual components. As a consequence, much is now known of the basal transcription complex. In contrast, less is known about the complexes formed at distal promoter elements. The c-fos SRE, for example, is known to bind Serum Response Factor (SRF) and ternary complex factors such as Elk-1. Their interaction with other factors at the SRE is implied but, to date, none have been identified. Here we describe the use of mass-spectrometric sequencing to identify six proteins, SRF, Elk-1 and four novel proteins, captured on SRE duplexes linked to magnetic beads. This approach is generally applicable to the characterisation of nucleic acid-bound protein complexes and the post-translational modification of their components.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.