Embryonic stem (ES) cells are able to grow indefinitely (self-renewal) and have the potential to differentiate into all adult cell types (pluripotency). The regulatory network that controls pluripotency is well characterized, whereas the molecular basis for the transition from self-renewal to the differentiation of ES cells is much less understood, although dynamic epigenetic gene silencing and chromatin compaction are clearly implicated. In this study, we report that UTF1 (undifferentiated embryonic cell transcription factor 1) is involved in ES cell differentiation. Knockdown of UTF1 in ES and carcinoma cells resulted in a substantial delay or block in differentiation. Further analysis using fluorescence recovery after photobleaching assays, subnuclear fractionations, and reporter assays revealed that UTF1 is a stably chromatin-associated transcriptional repressor protein with a dynamic behavior similar to core histones. An N-terminal Myb/SANT domain and a C-terminal domain containing a putative leucine zipper are required for these properties of UTF1. These data demonstrate that UTF1 is a strongly chromatin-associated protein involved in the initiation of ES cell differentiation.

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Transforming growth factor ␤ is the prototype of a large family of secreted factors that regulate multiple biological processes. In the immune system, TGF␤ acts as an anti-inflammatory and immunosuppressive molecule, whereas the cytokine interleukin (IL)-1␤ is a crucial mediator of inflammatory responses and induces proinflammatory genes and acute phase proteins. Here, we present evidence for the existence of a direct inhibitory interaction between the IL-1␤ and TGF␤ signaling cascades that is not dependent on IL-1␤-induced SMAD7 expression. IL-1␤ and its downstream mediator TAK1 inhibit SMAD3-mediated TGF␤ target gene activation, whereas SMAD3 nuclear translocation and DNA binding in response to TGF␤ are not affected. IL-1␤ transiently induces association between TAK1 and the MAD homology 2 domain of SMAD3, resulting in SMAD3 phosphorylation. Furthermore, IL-1␤ alleviates the inhibitory effect of TGF␤ on in vitro hematopoietic myeloid colony formation. In conclusion, our data provide evidence for the existence of a direct inhibitory effect of the IL-1␤-TAK1 pathway on SMAD3-mediated TGF␤ signaling, resulting in reduced TGF␤ target gene activation and restored proliferation of hematopoietic progenitors.

Rate and extent of spontaneous and induced chromosome loss have been determined at the callus level of somatic hybrids of mutants of Solanum tuberosum and Nicotiana plumbaginifolia. AEC (amino ethyl cystein) resistance in potato and Nitrate-Reductase deficiency in N. plumbaginifolia have been used as genetic markers and chromosome morphology as a cytological marker. In this combination, development of hybrid callus was late and slow. Only a limited number of non-regenerable hybrid calli have become available. Chromosome loss could clearly be established in these hybrids from loss of markers and from chromosome cytology. Loss of markers occurred independantly.The best conditions to induce loss of chromosomal material in donor cells by irradiation were found by cytological investigations. A very drastic reduction in chromosome transfer by fusion could be effected by irradiation of plant tissue and subsequent preparation of protoplasts after a few days. Following fusion, hybrid callus was recovered with the potato genome drastically reduced. The amount of loss was deduced from the presence of a few fragments in metaphase cells or from interphase nuclei after in situ hybridization with a repetitive potato DNA probe.

Single-nucleotide polymorphisms (SNPs) are single-nucleotide sequence variations between individuals. Two missense SNPs are present in the human undifferentiated embryonic-cell transcription factor 1 (UTF1) gene and their consequences for UTF1 function are investigated in this study. Expression of the UTF1 gene is restricted to pluripotent cells and UTF1 is a chromatin-associated protein with core histone-like properties. UTF1 further acts as a transcriptional repressor and is required for proper differentiation of pluripotent cells. Two missense mutations in UTF1 are reported: rs11599284, which results in a glycine to an arginine change at amino acid 73, and rs4480453, resulting in a leucine to methionine change at amino acid 275. To study the effects of these two SNPs, P19CL6 mouse embryonic carcinoma cells stably expressing eGFP-hUTF1 constructs containing either one or both SNPs were generated. The single and double SNPs did not alter the localization or transcriptional repressor activity of the protein. Further, the single SNPs did not alter the chromatin association and mobility of hUTF1. However, the double mutant, G73R/L275M, demonstrated a decreased chromatin association, indicating a degree of protein malfunction.