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51.
Suppression of src transformation by overexpression of full-length GTPase-activating protein (GAP) or of the GAP C terminus. 总被引:29,自引:17,他引:12
Overexpression of the full-length GTPase-activating protein (GAP) has recently been shown to suppress c-ras transformation of NIH 3T3 cells but not v-ras transformation (36). Here, we show that focus formation induced by c-src was inhibited by approximately 80% when cotransfected with a plasmid encoding full-length GAP. In a similar assay, focus formation by the activated c-src (Tyr-527 to Phe) gene was inhibited by 33%. Cotransfection of the GAP C terminus coding sequences (which encode the GTPase-accelerating domain) with c-src or c-src527F inhibited transformation more efficiently than did the full-length GAP, while the GAP N terminus coding sequences had no effect on src transformation. When cells transformed by c-ras, c-src, c-src527F, or v-src were transfected with GAP or the GAP C terminus sequence in the presence of a selectable marker, 40 to 85% of the resistant colonies were found to be morphologically revertant. The GAP C terminus induced reversion of each src-transformed cell line more efficiently than the full-length GAP, but this was not the case for reversion of c-ras transformation. Biochemical analysis of v-src revertant subclones showed that the reversion correlated with overexpression of full-length GAP or the GAP C terminus. There was no decrease in the level of pp60src expression or the level of protein-tyrosine phosphorylation in vivo. We conclude that GAP can suppress transformation by src via inhibition of endogenous ras activity, without inhibiting in vivo tyrosine phosphorylation of cellular proteins induced by pp60src, and that src may negatively regulate GAP's inhibitory action on endogenous ras. 相似文献
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Oxalyl-CPG: a labile support for synthesis of sensitive oligonucleotide derivatives. 总被引:11,自引:10,他引:1 下载免费PDF全文
A procedure is described for linking nucleosides covalently to controlled pore glass or cross-linked polystyrene supports by means of an oxalyl anchor. Though stable to triethylamine and diisopropylamine, the nucleoside-oxalyl link can be cleaved within a few minutes at room temperature with ammonium hydroxide in methanol. This new anchor can be used in automated synthesis of conventional oligonucleotides. The primary value, however, is that it enables one to employ solid support methodology to synthesize a variety of base-sensitive oligonucleotide derivatives, as illustrated here by synthesis of oligomers with base protecting groups intact and with methyl phosphotriester groups at the internucleoside links. 相似文献
54.
Osteogenesis imperfecta due to recurrent point mutations at CpG dinucleotides in the COL1A1 gene of type I collagen 总被引:7,自引:3,他引:4
Charles J. Pruchno Daniel H. Cohn Gillian A. Wallis Marcia C. Willing Barbra J. Starman Xiaoming Zhang Peter H. Byers 《Human genetics》1991,87(1):33-40
Summary Most individuals with osteogenesis imperfecta (OI) are heterozygous for dominant mutations in one of the genes that encode the chains of type I collagen. Each of the more than 30 mutations characterized to date has been unique to the affected member (s) of the family. We have determined that two individuals with a progressive deforming variety of OI, OI type III, have the same new dominant mutation [1(I)gly154 to arg] and that two unrelated infants with perinatal lethal OI, OI type II, share a second new dominant muation [1(I)gly1003 to ser]. These mutations occurred at CpG dinucleotides, in a manner consistent with deamination of a methylated cytosine residue, and raise the possibility that CpG dinucleotides are common sites of recurrent mutations in collagen genes. Further, these findings confirm that the OI type-III phenotype, previously thought to be inherited in an autosomal recessive manner, can result from new dominant mutations in the COL1A1 gene of type-I collagen. 相似文献
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Regulation of the synthesis of acetylcholine 总被引:1,自引:0,他引:1