PubMed · 7765523
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E Koller. 1994. Fluorogenic substrates for enzyme analysis.. https://pubmed.ncbi.nlm.nih.gov/7765523/
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Transgenic mice expressing human T cell leukemia virus type I (HTLV-I)-tax under the control of HTLV-I-long terminal repeat (LTR) promoter develop skeletal abnormalities with high bone turnover and myelofibrosis. In these animals, Tax is highly expressed in bone with a pattern of expression restricted to osteoclasts and spindle-shaped cells within the endosteal myelofibrosis. To test the hypothesis that lineage-specific transcription factors promote transgene expression from the HTLV-I-LTR in osteoclasts, we first examined tax expression in transgenic bone marrow cultures. Expression was dependent on 1alpha,25-dihydroxycholecalciferol and coincided with tartrate-resistant acid phosphatase (TRAP) expression, a marker of osteoclast differentiation. Furthermore, Tax was expressed in vitronectin receptor-positive mononuclear precursors as well as in mature osteoclast-like cells (OCLs). Consistent with our hypothesis, electrophoretic mobility shift assays revealed the presence of an OCL nuclear factor (NFOC-1) that binds to the LTR 21-base pair direct repeat, a region critical for the promoter activity. This binding is further enhanced by Tax. Since NFOC-1 is absent in macrophages and conserved in osteoclasts among species including human, such a factor may play a role in lineage determination and/or in expression of the differentiated osteoclast phenotype.
An Aspergillus gene coding for a pH 2.5 acid phosphatase enzyme was successfully overexpressed in Trichoderma reesei under the strong main cellobiohydrolase I (cbh 1) promoter. The best transformants produced up to 240 times more of the acid phosphatase than the Aspergillus strain from which the phosphatase gene was originally isolated. The recombinant enzyme was effectively secreted into the culture medium both by its own and the cbh 1 secretion signal. The heterologous pH 2.5 acid phosphatase enzyme produced by the Trichoderma transformants was seen as four protein bands of about 55-66 kD resulting from variable glycosylation in Trichoderma. The activity of the recombinant enzyme was not affected. Enzyme preparations rich in both cellulose and phytate hydrolysing enzymes are of interest in the animal feed industry.
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