Lennart Hansson

The role of su(f) gene function and ecdysterone in transcription of glue polypeptide mRNAs in Drosophila melanogaster

SummaryThe effect of the l(1)su(f)ts67gmutation and ecdysterone on the expression of glue polypeptide genes in Drosophila melanogaster has been studied. Using cloned DNA harboring glue protein genes Sgs3, Sgs4, Sgs7, and Sgs8, and Northern blot hybridization we show that no or extremely reduced accumulation of RNAs from these genes occurs in mutant larvae shifted to 30°C before and through 70 h after oviposition. On the other hand, a shift-up at 75 h or later results in the production of nearly normal amounts of these RNAs 48 h after shift-up. The results indicate functions of the su(f) gene other than suppression of forked bristles, namely that it is essential early in the third instar for the later transcription of the glue polypeptide genes. We also show that administration of exogenous ecdysterone to hormone deficient larvae induces transcription of Sgs3, Sgs4, Sgs7, and Sgs8 RNAs.

Effect of the l(1)su(f)ts67g mutation ofDrosophila melanogaster on glue protein synthesis

SummaryThe l(1)su(f)ts67g mutation has been shown to suppress the developmentally regulated expression of glue protein genes at 30°C. Transferring mutant larvae to the restrictive temperature before the end of the second larval instar results in the absence or extreme reduction of glue protein synthesis while general protein synthesis is unaffected. At the same time, the three glue protein correlated chromosomal regions 3C, 25B, and 68C continue to show prominent puffs. The results suggest that the mutation may be affecting the processing or translatability of specific mRNAs rather than the translational machinery itself.

Structure of the human β-casein encoding gene

Abstract The entire human β-casein-encoding gene, Bca, was cloned and sequenced. The gene consists of eight exons ranging from 21 to 531 nucleotides (nt) in length and extending over 10466 nt. Exon-2 contains the translational start, the entire signal sequence and the codons for the two first amino acids of the mature protein. This corresponds to the organization found in other species. The translational stop is localized to exon-7. Exon/intron boundaries are in accordance with the AG/GT rule and conform to suggested consensus sequences. Splice junctions are located between coding triplets. In all other species analyzed, Bca has been found to consist of nine exons; however, within intron-2 of the human gene, a sequence omitted from human mRNA, but corresponding to exon-3 of other known Bca genes, was revealed.

Ecdysterone responsive functions in the mutantl(1)su(f)ts67g ofDrosophila melanogaster

SummaryTransferring the temperature sensitive mutantl(1)su(f)ts67g from 25° C to 30° C before or early in the third larval instar blocks the increase in the ecdysterone titer that normally occurs at the end of the larval period. Feeding exogenous ecdysterone to these hormone-deficient larvae results in the formation of pseudopupae. The mutant was used to study ecdysterone-inducible functions in late larval salivary glands by preparing three animal samples with different hormone titers: the titer was low in one sample because of an earlier temperature shift, high in a second sample because the larvae were subsequently transferred to ecdysterone-supplemented food, and also high in a third sample that was kept at 25°C, providing a control for normal development. The effect of the different hormone conditions was studied by35S-methionine labeling of the salivary gland proteins during the larval to prepupal transition and the prepupal period. The results indicate that synthesis of several of the proteins normally appearing during the transition and prepupal period is induced by exogenous ecdysterone.

Carbohydrate specificity of theEscherichia coli P-pilus papG protein is mediated by its N-terminal part

The adherence of pyelonephritic Escherichia coli isolates to mammalian host cells is mediated by the P-pili structures on the bacterial surface. The protein constituting the distal part of the pili structure, papG, interacts with glycan receptors on the host cell. Variation in specificity for different glycoconjugates between the isolates, that may reflect variation in host tropism, has been correlated to three different classes of papG. Truncated variants of the class I, II and III papG adhesins were produced as fusion protein in E. coli and analysed for carbohydrate binding. The results showed that both carbohydrate binding and specificity of the papG adhesin resided in a linear part of the N-terminus of the protein.

Cloning and sequencing of human K-casein cDNA

A cDNA encoding kappa-casein of human milk was cloned and sequenced. The kappa-casein cDNA was isolated from a lambda gt11 library generated from mRNA prepared from a mammary gland biopsy obtained from a lactating woman. The library was screened with polyclonal rabbit antibodies raised against purified native kappa-casein. The obtained nucleotide sequence contained an ORF sufficient to encode the entire amino acid sequence of a kappa-casein precursor protein consisting of 182 amino acids. This includes a tentative signal peptide of 20 amino acids and a processed protein of 162 amino acids.