MCP::p65(m)::HSF1 consists of the coat protein of the MS2 RNA bacteriophage (Tag:MCP) fused to two transcription activation domains: one from the Mus musculus 'p65' gene (Rela, MGI:MGI:103290) and one from the Homo sapiens HSF1 gene (HGNC:5224). MCP::p65(m)::HSF1 is used as a component of the synergistic activation mediator (SAM) system, to produce effective transcriptional activation of a gene of interest. In the SAM system, three components are combined: 1. an artificial transcriptional activator containing a nuclease-dead form of Cas9 (such as dCas9::VP64), 2. an sgRNA into which two Tag:MS2 stem loops have been inserted (one on the tetraloop and one on stem loop 2) and which targets sequence upstream of the gene of interest, and 3. a second transactivator protein (such as MCP::p65(m)::HSF1) which includes the Tag:MCP tag. The sgRNA targets the dCas9-containing component to the target site upstream of the gene of interest, while the Tag:MCP tag in MCP::p65(m)::HSF1 binds specifically to the Tag:MS2 stem loop in the sgRNA, recruiting it to the assembled SAM complex (PMID:25494202). MCP::p65(m)::HSF1 has been shown to be effective as part of the SAM system in transgenic Drosophila ('flySAM', FBrf0238848) when combined with dCas9::VP64.