Stat Protein Transactivation Domains Recruit p300/CBP through Widely Divergent Sequences

Abstract

The signal transduction and activator of transcription (Stat) gene family has been highly conserved throughout evolution. Gene duplication and divergence has produced 7 mammalian Stat genes, each of which mediates a distinct process. While some Stat proteins are activated by multiple cytokines, Stat2 is highly specific for responses to type I interferon. We have cloned mouse Stat2 and found that while its sequence was more divergent from its human homologue than any other mousehuman Stat pairs, it was fully functional even in human cells. Overall sequence identity was only 69%, compared with 85-99% similarity for other Stat genes, and several individual domains that still served similar or identical functions in both species were even less well conserved. The coiled-coil domain responsible for interaction with IRF9 was only 65% identical and yet mouse Stat2 interacted with either human or mouse IRF9; the carboxyl terminus was only 30% identical and yet both regions functioned as equal transactivation domains. Both mouse and human transactivation domains recruited the p300/CBP coactivator and were equally sensitive to inhibition by adenovirus E1A protein. Interestingly, the Stat3 carboxyl terminus also functioned as a transactivator capable of recruiting p300/CBP, as does the Stat1 protein, although with widely differing potencies. Yet these proteins share no sequence similarity with Stat2. These data demonstrate that highly diverged primary sequences can serve similar or identical functions, and that the minimal regions of similarity between human and mouse Stat2 may define the critical determinants for function.

STAT proteins: novel molecular targets for cancer drug discovery

“…This information could be the basis for rational design of arti®cial competitors of STAT DNAbinding activity. Speci®c cooperative contacts of STATs with transcription coactivators, p48 (Bluyssen and Levy, 1997; Martinez-Moczygemba et al, 1997), CBP/p300 (Paulson et al, 1999;Zhang et al, 1996b), Sp1 (Cantwell et al, 1998), or with nuclear adaptor proteins (Rhodes et al, 2000), are also essential for their transcriptional activity (Bromberg and Darnell, 2000). Regions of STATs identi®ed to participate in cooperative interactions with other proteins include the coiled-coil domain and the C-terminal region (Paulson et al, 1999) distant from the DNA contact sites .…”

“…Speci®c cooperative contacts of STATs with transcription coactivators, p48 (Bluyssen and Levy, 1997; Martinez-Moczygemba et al, 1997), CBP/p300 (Paulson et al, 1999;Zhang et al, 1996b), Sp1 (Cantwell et al, 1998), or with nuclear adaptor proteins (Rhodes et al, 2000), are also essential for their transcriptional activity (Bromberg and Darnell, 2000). Regions of STATs identi®ed to participate in cooperative interactions with other proteins include the coiled-coil domain and the C-terminal region (Paulson et al, 1999) distant from the DNA contact sites . The conserved N-terminal regions of some STATs are also required for cooperative DNA binding of two STAT dimers (Xu et al, 1996), giving STATs the ability to induce genes with variations of the consensus binding site in promoters even though the a nity for binding to such sequences may be weak.…”

STAT3- and DNA methyltransferase 1-mediated epigenetic silencing of SHP-1 tyrosine phosphatase tumor suppressor gene in malignant T lymphocytes

“…We performed ChIP assays by using STAT3, DNMT1, and HDAC1 antibodies. Binding of two closely related proteins p300 and CBP that display histone acetylase activity (19), interact with STATs (20), and are expressed by malignant T cells and associate with STAT3 (data not shown) was also examined. Immunoprecipitation was followed by PCR with primers SHP-1 promoter 2-specific primers; SHP-1 gene exon 16-detecting primers served as a control.…”

Pre-assembly of STAT4 with the human IFN-α/β receptor-2 subunit is mediated by the STAT4 N-domain

“…Here, IFN-α/β-induced STAT4 tyrosine phosphorylation was found to be dependent upon the presence of human STAT2 (Farrar et al, 2000b). Unlike other STAT family members, STAT2 is highly divergent between mouse and human, and this dissimilarity is particularly striking within the COOH-terminal transactivation domain (Farrar et al, 2000a;Park et al, 1999;Paulson et al, 1999). The sequence divergence in STAT2 is functionally relevant because expression of the murine STAT2 molecule failed to restore IFN-α/β-dependent STAT4 phosphorylation in human STAT2-deficient cells (Farrar et al, 2000a).…”