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Vincent Anquetil Caroline Le Sommer Agn��s M��reau Sandra Hamon Hubert Lerivray Serge Hardy 《The Journal of biological chemistry》2009,284(47):32370-32383
Alternative splicing of 3′-terminal exons plays a critical role in gene expression by producing mRNA with distinct 3′-untranslated regions that regulate their fate and their expression. The Xenopus α-tropomyosin pre-mRNA possesses a composite internal/3′-terminal exon (exon 9A9′) that is differentially processed depending on the embryonic tissue. Exon 9A9′ is repressed in non-muscle tissue by the polypyrimidine tract binding protein, whereas it is selected as a 3′-terminal or internal exon in myotomal cells and adult striated muscles, respectively. We report here the identification of an intronic regulatory element, designated the upstream terminal exon enhancer (UTE), that is required for the specific usage of exon 9A9′ as a 3′-terminal exon in the myotome. We demonstrate that polypyrimidine tract binding protein prevents the activity of UTE in non-muscle cells, whereas a subclass of serine/arginine rich (SR) proteins promotes the selection of exon 9A9′ in a UTE-dependent way. Morpholino-targeted blocking of UTE in the embryo strongly reduced the inclusion of exon 9A9′ as a 3′-terminal exon in the endogenous mRNA, demonstrating the function of UTE under physiological circumstances. This strategy allowed us to reveal a splicing pathway that generates a mRNA with no in frame stop codon and whose steady-state level is translation-dependent. This result suggests that a non-stop decay mechanism participates in the strict control of the 3′-end processing of the α-tropomyosin pre-mRNA. 相似文献
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The effective elastance of the respiratory system (which has been previously shown to provide an index of the ability of the respiratory musculature to compensate rapidly for transient mechanical ventilatory loads) was measured in six hypoxic dogs to determine whether hypoxia hindered immediate load-compensatory mechanisms. The effective elastance value was computed from measurements of control tidal volume and the pressure developed at the airway opening during the first inspiratory effort following airway occlusion at FRC. The mean effective elastance was 197 cmH2O/l while the animals were breathing room air and did not change significantly when the animals were rendered hypoxic by reducing the inspired oxygen concentration, in five dogs, or by controlled hemorrhage, in two dogs. It was concluded that inasmuch as effective elastance measurements remain constant during hypoxia, the stability of ventilation is not significantly impaired in this situation. 相似文献
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Cervicofacial rhytidectomy 总被引:1,自引:0,他引:1
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Size of the directing moiety at carbon 5 of cytosine and the activity of human DNA(cytosine-5) methyltransferase 总被引:3,自引:0,他引:3
T A Hardy D J Baker E M Newman L C Sowers M F Goodman S S Smith 《Biochemical and biophysical research communications》1987,145(1):146-152
M13 DNAs in which carbon 5 of each deoxycytidine residue in one strand is replaced with a bulky group are very good substrates for human DNA (cytosine-5) methyltransferase. Rate enhancements of up to 35 fold are obtained depending on the size of the moiety at C-5. The enzyme appears optimally suited to sense a methyl group in one strand at this position. Alkaline density gradient analyses of the distribution of methyl groups applied to 5-BrdCyd or 5-IdCyd substituted DNA reveal that these groups serve to direct the enzyme to methylate the unsubstituted strand. 相似文献