The signal sequence of the p62 protein of Semliki Forest virus is involved in initiation but not in completing chain translocation

An intermediate construct, analogous to pGEM2alphaGX, and also conraining a unique Xho I site, was needed for the constructions of dhfrcontaining plasmids. For this purpose we inserted the Xho I linker into partially Xmn I cut pGEM2dhfr (Zerial et al., 1986) . After cutting the linkers, linear plasmid was purified on agarose gel and religated. Since the second Xmn I site in pGEM2dhfr is located in the beta-lactamase coding region of the vector (Snt~liffe, 1979) and insertion of an Xho I site by an octamer linker will result in an ampicillin-sensitive E. coli phenotype after transformation, only the desired pGEM2dhfrX construct was obtained. From this plasmid, an Xho I-Pvu' I fragment of at least 2,012 bp (the precise length of the cDNA insert, i.e., the length of the 3' untranslated region of dhfr, is not known in pGEM2dhfr) was used for the construction of pC62dhfr.