In the yeast Saccharomyces cerevisiae, the MADS-box protein Mcm1, which is highly related to mammalian SRF (serum response factor), forms a ternary complex with SFF (Swi five factor) to regulate the cell cycle expression of genes such as SWI5, CLB2 and ACE2. Here we show that the forkhead protein Fkh2 is a component of SFF and is essential for ternary complex formation on the SWI5 and ACE2 promoters. Fkh2 is essential for the correct cell cycle periodicity of SWI5 and CLB2 gene expression and is phosphorylated with a timing that is consistent with a role in this expression. Furthermore, investigation of the relationship between Fkh2 and a related forkhead protein Fkh1 demonstrates that these proteins act in overlapping pathways to regulate cell morphology and cell separation. This is the first example of a eukaryotic transcription factor complex containing both a MADS-box and a forkhead protein, and it has important implications for the regulation of mammalian gene expression.

BackgroundAbiotic stresses which include drought and heat are amongst the main limiting factors for plant growth and crop productivity. In the field, these stress types are rarely presented individually and plants are often subjected to a combination of stress types. Sorghum bicolor is a cereal crop which is grown in arid and semi-arid regions and is particularly well adapted to the hot and dry conditions in which it originates and is now grown as a crop. In order to better understand the mechanisms underlying combined stress tolerance in this important crop, we have used microarrays to investigate the transcriptional response of Sorghum subjected to heat and drought stresses imposed both individually and in combination.ResultsMicroarrays consisting of 28585 gene probes identified gene expression changes equating to ~4% and 18% of genes on the chip following drought and heat stresses respectively. In response to combined stress ~20% of probes were differentially expressed. Whilst many of these transcript changes were in common with those changed in response to heat or drought alone, the levels of 2043 specific transcripts (representing 7% of all gene probes) were found to only be changed following the combined stress treatment. Ontological analysis of these ‘unique’ transcripts identified a potential role for specific transcription factors including MYB78 and ATAF1, chaperones including unique heat shock proteins (HSPs) and metabolic pathways including polyamine biosynthesis in the Sorghum combined stress response.ConclusionsThese results show evidence for both cross-talk and specificity in the Sorghum response to combined heat and drought stress. It is clear that some aspects of the combined stress response are unique compared to those of individual stresses. A functional characterization of the genes and pathways identified here could lead to new targets for the enhancement of plant stress tolerance, which will be particularly important in the face of climate change and the increasing prevalence of these abiotic stress types.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-456) contains supplementary material, which is available to authorized users.

SSX genes show extensive nucleotide sequence conservation but little is known of their function. Disruption of SSX1 or SSX2, by chromosome translocation and`inframe' fusion to SYT, is a consistent feature of synovial sarcomas. The resulting SYT-SSX1/SSX2 proteins are activators of transcription; transactivation function is located in SYT. Unrearranged SSX1 can repress transcription, and this has been attributed to a putative KruÈ ppel associated box (KRAB) repression domain at the N-terminus. Here we isolated SSX-KRAB domains to speci®cally measure repression activity, using a previously characterized KOX1-KRAB domain as a control. In our repressor assay SSX1-and SSX2-KRAB domains down-modulated the transactivation of a reporter gene by threefold, compared with 83-fold repression achieved by KOX1-KRAB in the assay. Yeast two-hybrid analysis showed that SSX1-KRAB, unlike KOX1-KRAB, fails to interact with the KRAB corepressor TIF1b. These results raise questions about the evolutionary and functional relationship of SSX-KRAB and typical KRAB domains of KruÈ ppel zinc ®nger genes. We found that full-length SSX1 showed potent (74-fold) repression in our repressor assay, indicating the existence of a repression domain distinct from SSX-KRAB. By assaying deletion constructs of SSX1 we localized repression activity to 33 amino acids at the C-terminus. This novel domain is conserved between SSX family members, and, unlike the KRAB-related domain, is retained on fusion with SYT. This has important implications in understanding the mechanism by which the SYT-SSX fusion protein could contribute to neoplasia.Keywords: sarcoma; SSX; KRAB; transcription Chromosome translocation t(X;18)(p11.2;q11.2) (Clark et al., 1994;Crew et al., 1995) is a diagnostic feature of human synovial sarcomas, in some cases representing the sole cytogenetic abnormality (Sandberg and Bridge, 1994). All the available evidence indicates that this translocation is a key event in tumorigenesis. In all tumours characterized, the SYT gene on chromosome 18 is juxtaposed`in-frame' with either the SSX1 gene or SSX2 gene on chromosome X (Figure 1). SSX1 and SSX2 are now known to be members of a highly conserved multigene family Gure et al., 1997), and the SSX loci that have been mapped are all located in chromosome band Xp11.2 (Crew et al., 1995;. In contrast to SYT, which is a widely expressed gene (de Bruijn et al., 1996; J Knight., unpublished data), SSX transcripts show a very restricted distribution in adult human tissues. So far, SSX1 and SSX2 expression has only been detected in testis and thyroid (Crew et al., 1995;Tureci et al., 1996;Gure et al., 1997).As yet, little is known about the normal biological functions of the SYT and SSX gene products. No DNA binding sequences are recognizable in the SYT or SSX proteins. However, when coupled to a GAL4 DNA binding domain in in vitro reporter assays, SYT can activate transcription (70-fold activation) and SSX1 can repress transcription (50-fold repression) from a minimal promoter in NIH3T3 ®broblasts (Brett ...

The solution structure of the 33 kDa complex between the dimeric DNA-binding core domain of the transcription factor MEF2A (residues 1±85) and a 20mer DNA oligonucleotide comprising the consensus sequence CTA(A/T) 4 TAG has been solved by NMR. The protein comprises two domains: a MADS-box (residues 1±58) and a MEF2S domain (residues 59± 73). Recognition and speci®city are achieved by interactions between the MADS-box and both the major and minor grooves of the DNA. A number of critical differences in protein±DNA contacts observed in the MEF2A±DNA complex and the DNA complexes of the related MADS-box transcription factors SRF and MCM1 provide a molecular explanation for modulation of sequence speci®city and extent of DNA bending (~15 versus~70°). The structure of the MEF2S domain is entirely different from that of the equivalent SAM domain in SRF and MCM1, accounting for the absence of cross-reactivity with other proteins that interact with these transcription factors.

White adipose tissue exhibits inflammation as tissue mass expands in obesity, involving macrophage infiltration and a direct inflammatory response by adipocytes. DNA microarrays and conditioned medium have been used to examine the effects of macrophages on global gene expression in human adipocytes. SGBS adipocytes, differentiated in culture, were treated with macrophage-conditioned medium (U937 cells) for 4 or 24 h; control cells received unconditioned medium. Agilent arrays comprising 44,000 probes were used to analyse gene expression. Microarray analysis identified 1,088 genes differentially expressed in response to the conditioned medium at both 4 and 24 h (754 up-regulated, 334 down-regulated at 24 h); these included genes associated with inflammation and macrophage infiltration. A cluster of matrix metalloproteinase genes were highly up-regulated at both time-points, including MMP1, MMP3, MMP9, MMP10, MMP12 and MMP19. At 4 and 24 h, MMP1 was the most highly up-regulated gene (>2,400-fold increase in mRNA at 24 h). ELISA measurements indicated that substantial quantities of MMP1 and MMP3 were released from adipocytes incubated with conditioned medium, with little release by control adipocytes. Treatment with TNFalpha induced substantial increases in MMP1 (>100-fold) and MMP3 (27-fold) mRNA level and MMP1 and MMP3 release in adipocytes, suggesting that this cytokine could contribute to the stimulation of MMP expression by macrophages. In conclusion, macrophage-secreted factors induce a major inflammatory response in human adipocytes, with expression of MMP family members being strongly up-regulated. The induction of MMP1 and other MMPs suggests that macrophages stimulate tissue remodelling during adipose tissue expansion in obesity.