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B7-1 is one of the co-stimulatory factors which plays an important role in immunity. We have cloned and functionally mapped the promoter of the murine B7-1 gene using transient transfection assays in mouse L (tk-) cells. The B7-1 basal promoter consists of three positively regulated regions. The distal region, located at -2597 to -1555, contains an assortment of putative transcription factor binding sites. The proximal upstream region, located at -130 to -110, contains a tandem repeat sequence 5'-GTGTTCTAGTGTT-3'. A downstream region is positioned at +269 to +25. We have also identified an alternatively spliced form of the murine B7-1 gene in L (tk-) cells.

Partial cDNA clones generated by RT-PCR were used as probes to clone the cDNAs encoding the human alpha 4 and beta 2 neuronal nicotinic acetylcholine receptor (nAChR) subunits. The 2.1-kb alpha 4 cDNA shows 84 and 76% identity to the rat and chicken cDNA sequences, respectively. The deduced amino-acid sequence shares 89 and 84% similarity, respectively, with the corresponding rat and chicken proteins, with most of the divergence occurring in the cytoplasmic domain. The 1721-nucleotide beta 2 sequence was identical to the human beta 2 sequence previously reported. Transfection of the alpha 4 and beta 2 clones into HEK293 cells resulted in the formation of binding sites that display high affinity towards [3H] cytisine, a characteristic of the alpha 4 beta 2 subtype produced in vivo.

The identification of a sorbitol-induced sorbitol dehydrogenase (SDH) activity from Saccharomyces cerevisiae is described. The SDH1 structural gene was isolated from a lambda gt11 yeast genomic library using an antibody to a 40-kDa protein induced in yeast cells growing in medium containing sorbitol. The gene encodes a 357-amino-acid (aa) protein deduced from the nucleotide sequence. Comparison of the aa sequence of the yeast SDH1 with that of sheep liver SDH reveals a 63% overall similarity. Yeast transformants containing the cloned gene carried on a multicopy plasmid express high levels of SDH1 only when grown on sorbitol, suggesting that the cloned gene contains both regulatory and coding sequences.

We have isolated and characterized a gene encoding the phytochrome polypeptide of Avena. Based on nucleotide sequence identity with previously sequenced cDNA clones this gene is designated as type 3 (phy3). The gene is about 5.9 kb long with six exons and five introns, one each of the latter in the 5' and 3'-untranslated regions. The largest exon encodes the entire 74-kDa, chromophore-bearing, N-terminal domain of the photo-receptor postulated to be directly involved in its mechanism of action. The transcription start point, identified by mung-bean nuclease digestion, is located 24 to 35 bp downstream from a tandem TATA box. Sequence elements homologous to a number of motifs implicated as upstream regulatory elements in other genes are present in the 5'-flanking DNA of phy3. Particularly intriguing are three elements at positions -140, -470 and -650. These elements share homology with the 'GT' motif postulated to be a component of the light-regulatory element of genes encoding the small subunit of ribulose bisphosphate carboxylase.