Article Abstract:
The bHLH-PAS transcription factor SIM1, which is expressed during development of the hypothalamic-pituitary axis, is necessary for development of neuroendocrine lineages. SIM1 is expressed in three hypothalamic nuclei, the supraoptic nucleus (SON), the anterior periventricular nucleus (aPV), the paraventricular nucleus (PVN). SIM1 acts upstream to maintain Brn2 expression. The expression then directs terminal differentiation of specific neuroendocrine lineages in the PVN/SON. There is evidence that in development of Sim1 mutant hypothalamus, the prospective PVN/SON region does not express Brn2. Mice with a null allele of Sim1 were produced to study Sim1 function in the hypothalamus. The SON and PVN of the mice are hypocellular. At the final stages of their differentiation, SIM1 controls the development of five types of secretory neurons.
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Article Abstract:
SCL/Tal-1 is a transcription factor needed for hematopoietic stem cell differentiation. SCL shows up in endothelial and neural progenitors, but SCL function in those cells is not known. SCL expression in zebrafish mutant cloche (clo) is almost nonexistent in vascular and hematopoietic tissues. It has been shown that clo does not differentiate angioblasts and blood. Genetic analysis shows that the clo mutation and the SCL locus are not linked. Forced expression of SCL in clo embryos gets rid of vascular and blood defects. That indicates that SCL acts downstream to call for vascular/hematopoietic differentiation.
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Article Abstract:
Tat-Sf1, an HIV-1 Tat cellular coactivator protein, is a transcription elongation factor of the general sort. It stimulates transcription elongation from the HIV-1 long terminal repeat (LTR) strongly and specifically. It provides a very useful in vitro model system to study the process. Protein-affinity chromatography has been used to identify cellular factors with important roles in transcription elongation. Results indicate that an ATP-inactivatable general elongation factor (AIEF) necessary for Tat-SF1 activity, and for which Tat can substitute in a functional way, exists.
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