Biomedical subjects

M W Saul

Publications and source records attributed to M W Saul.

3 recordsLinked to original sources

PubMed1992

Expression of a downstream gene from a bicistronic transcription unit in transgenic tobacco plants.

We have constructed a set of plasmids carrying an artificial compact stop-start codon sequence, TGATGTAACATGA, between an upstream open reading frame, terminating at one of the stop codons, and a downstream kanamycin-resistance (KmR)-encoding gene (nptII) initiating at the second ATG. These plasmids were introduced into tobacco protoplasts by direct gene transfer. The efficiency of expression of the downstream nptII gene was measured by scoring the number of KmR transformants. With a closer distance between the functional stop and start codons, a tendency to less efficient expression of nptII was found. The integration and expression of both genes as a bicistronic transcription unit were verified by Southern- and Northern-blot analyses. A possible application of the compact stop-start codon sequence for insertional mutagenesis is discussed.

Base Sequence↗

PubMed1991

Isolation and molecular characterization of PosF21, an Arabidopsis thaliana gene which shows characteristics of a b-Zip class transcription factor.

We have isolated a putative transcription factor gene, PosF21, from Arabidopsis thaliana using an indirect cross-hybridization approach. cDNA clones were isolated which encode single repeating amino acids. Such sequences may function as activation domains in transcription factors and may be indicative for such proteins. The clone PosF21 encodes a region very rich in glutamines. Besides this putative activation domain it encodes a protein sequence which shows all the characteristics of a basic-domain/leucine zipper type of DNA-binding domain. PosF21 is expressed constitutively at a low level in young seedlings and in roots, stems and leaves of mature Arabidopsis plants. A genomic clone of PosF21 was isolated and the gene structure was analyzed. Related sequences in Arabidopsis and a wide range of other plants were detected using the putative DNA-binding domain as a probe in cross-hybridization experiments. Transient transformations in tobacco protoplasts were performed using the beta-glucuronidase (GUS) gene as reporter gene. Approximately 400 bp of the 5' genomic region of PosF21 promote expression of the GUS gene in tobacco protoplasts. Evidence for a regulatory function of PosF21 was obtained since co-expression of the full PosF21 protein or its DNA-binding region alone specifically stimulated GUS gene expression directed from the PosF21 promoter by 6-8-fold.

Amino Acid Sequence↗

PubMed1979

ColE1 plasmid mobility: essential and conditional functions.

Sequences essential for the conjugal transfer of ColE1 can be divided into a cis-acting site and a region encoding trans-acting products. Each of these was successively cloned into a non-transmissible plasmid vector. The resulting chimera was transmissible by the conjugative plasmids F'lac,pro (incFI) and R64drd11 (incIalpha). The sequences encoding colicin E1, immunity, and incompatibility were absent from this chimera: therefore they are not essential for the conjugal transmission of the ColE1 plasmid. In contrast to ColE1, however, the same chimera was deficient in conjugal transfer initiated by R751 (incP) and R388 (incW). This suggests that ColE1 sequences other than those cloned in the chimeric plasmid are necessary for its mobilization by R751 and R388. Three such regions were revealed by screening a series of ColE1 insertion mutants for transfer by R751 and R388. Two of these regions encode no other known function while the third is encoded by a region which overlaps the gene for colicin E1 itself.

Conjugation, Genetic↗