Biomedical subjects

D Landsman

Publications and source records attributed to D Landsman.

59 records · Page 4Linked to original sources

PubMed1986

Chromosomal protein HMG-17. Complete human cDNA sequence and evidence for a multigene family.

Antibodies elicited against chromosomal protein HMG-17, purified from calf, were used to screen a human lambda gt11 cDNA expression library and isolate the full length cDNA coding for this protein. Sequence analysis reveals that the nucleotide distribution along this cDNA is highly asymmetric. The amino acid sequence, deduced from the reading frame, reveals that the human HMG-17 is, respectively, 96 and 92% homologous with the calf and chicken protein. The amino acid substitution are conservative suggesting evolutionary constraints on the conformation of the protein. The human genome contains 35-50 HMG-17 gene copies which, as revealed by Southern analysis, are distributed at several loci. Northern analysis of total RNA isolated from 3 human cell lines, indicates that each cell contains a single-size mRNA coding for this protein. Nucleotide sequences which cross-hybridize, under stringent conditions, with the human HMG-17 cDNA are present in the genome of rodents and absent from the genomes of sea urchin, Drosophila, and yeast. The availability of a probe for the HMG-17 gene may help elucidate the cellular role of this protein which may confer specific conformations to transcribable regions in the genome.

Amino Acid Sequence↗

PubMed1986

Immunofractionation of DNA sequences associated with HMG-17 in chromatin.

Antibodies specific for chromosomal protein HMG-17 were immobilized on CNBr-Sepharose and the resulting immunoaffinity column was used to purify chromatin segments enriched in HMG-17. The DNA was purified from both the nucleosomal fraction which was bound to the column and from the fraction which was not bound, and examined with DNA probes representing repetitive DNA, non-transcribed genes, transcribed genes and inducible genes. The results suggest that HMG-17 is preferentially associated with DNA sequences coding for genes, regardless of whether they are transcribed, and therefore support the notion that HMG-17 confers specific structural characteristics on selected regions in the genome.

Animals↗

PubMed1986

Exchange of proteins during immunofractionation of chromatin.

The migration and rearrangement of chromosomal proteins during immunofractionation of chromatin has been investigated. Oligonucleosomes from two different chromatins, chicken erythrocyte or rat liver, were mixed with oligonucleosomes from the other species which had been depleted of histones H1/H5 and high mobility group proteins (HMGs). The mixture was treated with buffers of various ionic strengths and immunofractionated on an anti-H1 degrees/H5 or anti-HMG-17 IgG-Sepharose column. The type of DNA, which was retained as the bound fraction on the column, was determined by slot blot analysis using nick-translated repetitive DNA probes from either chicken or rat. The results indicate that in low ionic strength buffers (i.e., below 40 mM NaCl), there is very little exchange of either histone H5 or HMG-17 among nucleosomes and therefore we suggest that it is possible to fractionate nucleosomes according to their antigenic content.

Animals↗

PubMedDate not supplied

Curved DNA in promoter sequences.

Sequence-dependent DNA curvature is known to play an important role in initiation of transcription of many genes. We compared the distribution of predicted intrinsic curvature of Escherichia coli and human promoter sequences with the distribution of curvature of randomly selected coding and non-coding fragments from these organisms. Different methods of curvature calculation were found to yield mostly similar overall tendencies of DNA curvature in all groups of sequences. According to all methods of calculation, E. coli promoters were found to be more curved than coding sequences from the same genome and random sequences with the same nucleotide composition. By contrast, the average curvature of human promoter sequences was only marginally greater than the average curvature of human coding sequences. Non-coding intron sequences were found to be the most curved of the human sequences examined. Based on these observations, we hypothesize about the role of DNA curvature in promoter sequences.

Computer Simulation↗

PubMedDate not supplied

New evidence that Candida albicans possesses additional ATP-binding cassette MDR-like genes: implications for antifungal azole resistance.

Emergence of resistance of Candida albicans to antifungal triazoles is increasingly recognized as an important cause of refractory mucosal candidiasis in HIV-infected patients. Recently, CDR1, which is thought to be analogous to the human MDR-1 P-glycoprotein, has been cloned in C. albicans. It has been proposed that its expression is partially responsible for fluconazole resistance in C. albicans. This gene is characterized by the presence of an ATP binding cassette (ABC) region and is distinct from the BENr gene which does not encode such a functional domain. As the molecular basis for fluconazole resistance appears to be multifactorial, we considered that there may be other ATP binding cassette-containing MDR genes that may potentially contribute to antifungal azole resistance in C. albicans. We therefore sought to identify potential target sequences that may be derived from candidate genes that share homology with the ATP binding cassette region of the human MDR-1 P-glycoprotein. Degenerate oligonucleotide primers based on the known sequence from the ATP binding cassette region of the human MDR-1 P-glycoprotein were used to amplify PCR products within the range of 100 bp in length from C. albicans isolates (3 fluconazole-susceptible and 3 fluconazole-resistant). Sequence analysis of individually subcloned PCR products, derived from the six isolates revealed 34 sequences in total. The results of our study identified 14 clones (with at least one per isolate) with a high degree of homology to the ATP binding cassette of the human MDR-1 P-glycoprotein. The BLAST search did not disclose homology of these new sequences to the C. albicans CDR1 gene, suggesting that C. albicans may possess more than one MDR-like gene. We conclude that C. albicans may possess one or more additional genes encoding ATP binding cassette MDR-like proteins that are distinct from CDR 1 and which could participate in the development of fluconazole resistance.

AIDS-Related Opportunistic Infections↗